LEIDSE GEOLOGISCHE deel 3-5-1967 MEDEDELINGEN, 40, pp. 1—74, published separately

Hydrology of the Upper-Garonne basin (Valle de Arán, )

BV

H. Rijckborst

Abstract

runoff Valle and mountain basin in the consists of The in the de Arán, which is a steep high , essentially baseflow, and fast runoff is only a minor phenomenon. related and forest, and the of the which contributes the fast The baseflow is to areas of scree percentage precipitation to runoff, is related to the area of barren rocks.

determined for It that The orographic precipitation pattern has been statistically eight valleys. was found, orographic precipita- mountain tion increases linearly with altitude, while the maximum increase occurs perpendicular to the slopes of the steep

The due of rainfall 1.50 above showed as a 10—15 error ranges. expected errors, to measurements at m ground level, percent in the balance. The Penman values corrected for and reliable water evaporation were snow evaporation they subsequently gave results.

Contents

Illustrations 2; Tables 3; Tables 1—45 Appendices 5.4 Wind 23

4; List of symbols 4; Abbreviations 5 5.5 Cloud cover 24

5.6 Relative air humidity 25

1. Introduction 7

1.1 The project 7 6. Precipitation analysis 25 1.2 Acknowledgments 7 6.1 Introduction 25

1.3 Location 7 6.2 Precipitation regime 25

1.4 History of the Valle de Aran 7 6.3 Variations in the annual precipitation 1946—

1966 26 1.5 Stream system 9 6.4 Relation of precipitation, wind direction and

cloud cover 28 2. Morphometry 9 6.5 The precipitation 28 2.1 Morphomctric data 9 map 6.6 of the rain orifice Height gauge 29 2.2 Influence of basin morphology onhypsometric 6.7 Regression analysis 30 curves 11 6.8 Major topographic features, which affect 2.3 Specific degradation 12 precipitation 31 2.4 Hypsometric integral 12 6.9 Precipitation on steep valley slopes 31 2.5 Erosion models 13 6.10 Snowfall 33 2.6 Origin of the Garonne 13 6.11 Snow duration 33 2.7 The Miocene planation level 14

6.12 Water content of fresh snow 35 2.8 Quaternary developments ofthe Vallede Aran 17 2.9 Slopes 17 7. Runoff 35

7.1 Introduction 35 3. Available meteorological data 18 7.2 Available data 35 3.1 Introduction 18 7.3 Stage-discharge relations 36 3.2 Precipitation and snowfall 18 7.4 Land classification and map morphological 3.3 Temperature, wind direction, wind velocity analysis 37 and cloud cover 19 7.5 to characteristics 39 Introduction runoff .... 3.4 Air and air 19 pressure humidity 7.6 of the Pontet de Rius basin 41 J-values .... 3.5 Unused records 19 7.7 Relation of runoff, land classification and

morphology in Pontet de Rius 42 4. of the Valle de- Aran 21 Climatology 7.8 J-values of the Aigüestortes basin 43 4.1 Introduction 21 7.9 J-values of the Upper Negro basin 43 4.2 Classification of the climates 21 7.10 Monthly runoff variation coefficients of eight 4.3 The effect of the the Valle de Pyrenees on representative drainage basins 45 Aran climate 21 7.11 Relation of variation coefficients, morpholo-

and land classification in gy eight drainage

5. Climatic elements 21 basins 45

5.1 Air 21 7.12 45 pressure frequency 5.2 Temperature 22 7.13 Flood routing through fourteen reservoirs in

the 5.3 Vertical temperature gradients 22 Upper Aiguamoix 48 2 H. Rijckborst: Hydrology of the Upper-Garonne basin

8. Evaporation 49 10.6 Groundwater flow through the ungrouted

8.1 Introduction 49 Aiguamoix dam foundations 61

8.2 Evaporation estimations from meteorological

data 49 11. Karst systems 61

8.3 Evaporation estimations from the snow cover 50 11.1 Introduction 61

8.4 Mountain shadow and orientation of the 11.2 Geology 62

50 11.3 The del valleys Güells Jueu system 62

8.5 Short wave radiation 51 11.4 measurements .... The Estua system 63

8.6 Actual evaporation estimations 53 11.5 The Ruda system 63

11.6 The Bó system 64

9. Glaciers of the 54 11.7 The group Pila system 64 9.1 Introduction 54 11.8 Tracer experiments 64

9.2 Precipitation on the glaciers 54 11.9 Chemical analyses 65

9.3 increase of the Monthly 0° C-isotherms ... 55 11.10 Runoff analysis 66 9.4 Snow depth and snow density 55 11.11 Infiltrationinto limestones 67

9.5 Evaporation from the glaciers 56

9.6 term variations of the 56 balance Long glaciers .... 12. Water 67

Water oftwo basins 67 12.1 balance selected . ...

10. The Aiguamoix dam 57 12.2 Water balance of eight basins 67

10.1 Introduction 57 Water the de Aran 68 12.3 balance of Valle ....

10.2 Topography and geology 58 12.4 Runoff ofthe Vallede Aran 69

10.3 Development of the project 58

10.4 Watertight screen and drainage ofthe founda- Conclusions 70

tions 58

10.5 Water permeability tests 60 References 71

ILLUSTRATIONS

1.1 Location of the Valle de Aran. 3.3 rain Mougin gauges. 1.2 The medieaval church of Bossost. 5.1 Mean air of Arties and monthly pressure (mb) Viella, 1.3 Tombstone of an Aráñese nobleman (church of Las compared with the Naca standard atmosphere.

Bordas) 12th 5.2 of station Viella and century. Monthly temperature the valley 1.4 Stream of the Garonne River. system the mountain station Bonaigua. 1.5 The karst spring Giiell del Garona where the 5.3 Annual fluctuation of temperature gradients during River Garonne originates. the period 1955—1965. 2.1 Hypsometric histograms of thirty-three basins. 5.4 Wind from the roses meteorological stations during 2.2 and distribu- Hypsometric histogram slope-altitude period 1955—1965. tion of the Valle de Aran. 5.5 Morning valley slope wind in the Valarties valley. 2.3 and distribu- Hypsometric histogram slope-altitude 6.1 Monthly precipitation coefficients for the valley tion of and thejueu- Aiguamoix-River. stations and mountain stations.

2.4 of three sections. Maps simplified valley cross 6.2 Maximum daily rain precipitation and rain duration 2.5 of three simplified valley Hypsometric histograms for Viella and Restanca (1955—1965).

cross sections for a and circular- rectangular-, elliptic- 6.3 of the de Aran Precipitation map Valle (1946—1966). . 6.4 Double mass curve of the Bonaigua precipitation 2.6 Hypsometric integral of the Valle de Aran, showing in and in rain measured a mougin gauge (y) a daily the volume of eroded material 100 altitude. per m gauge (x). 2.7 Results of the model analysis of the Valle de Aran. 6.5 Accumulated precipitation values of Bonaigua, show- 2.8 Structure-contour of the top Devonian in the map the 44 in the ing percent error measurements 4.40 m Valle de Aran. above ground level. 2.9 analysis of the Iñola basin, showing Morphometric 6.6 Relation of the annual average precipitation (mm) the dip of the Miocene planation level in the direc- and altitude (m) during the period 1946—1966. tion of the present river. 6.7 Relation of the annual snowfall and average (cm) 2.10 of Glaciation a Tertiary planation level. altitude (m) during the period 1946—1966. 2.11 Cross section of the Toran valley at the Lower Toran 6.8 Snowfall of the de Aran the map Valle during period damsite. 1946—1966. 2.12 Cross section of the Toran valley at the Upper Toran 6.9 Snow total of the to precipitation ratio map Valle damsite. de Aran during the period 1946—1966. 2.13 Distribution of the 100 weighted average slope per m 7.1 Distribution of runoff gauging stations and catch- altitude in ten drainage basins. the effect of karst of ment areas, showing systems. 2.14 Frequency weighted average slopes. 7.2 Bar runoff records the 2.15 Length profiles of the Valle de Aran and graph, showing during period 1046—1966. increase of drainage area in a downstream direction 7.3 for station 13 of the Garonne River. Stage-discharge curves runoff gauging

and 16 3.1 Location of meteorological stations. (Negro River) (Barrados River).

3.2 Bar graph, showing precipitation records from 1946— 7.4 Area-altitude distribution and hypsometric integral 1966. of the Pontet de Rius- and Aigiiestortes basins. Illustrations 3

7.5 Weir at station 20 and 3 and its stage-discharge rate 9.2 Average monthly rainfall and snowfall in the Aneto

relation. area.

7.6 Areas of land classification units in thirty-three 9.3 Position of the 0°C-isotherm in the Aneto area during the drainage basins. summer months.

7.7 Runoffanalysis of the Pontet de Rius basin. 9.4 Snow cover in the Lago Mar area (elev. 2200—3000 of in 7.8 Relation ofbaseflow and percentage the precipita- m) June 1965.

the fast runoff of the Pontet 9.5 Estimation of annual tion, contributing to de the average snow accumulation

Rius basin. on the Aneto glacier.

7.9 Length profile of the Valarties River upstream from 9.6 Areal extent of the Aneto glaciers in various periods

station 20. (1810, 1928, 1948 and 1958). 7.10 Average monthly runoff variation coefficients for 9.7 Longterm precipitation measurements (1922—1965)

eight basins. from Lés.

7.11 Relation of maximum runoff variation coefficients 10.1 of the dam. to Topographical map Aiguamoix land classification units. 10.2 Fluvio-glacial material in the left Aiguamoix bank at

7.12 Flood frequency at four stations in the Valle de Aran. the dam axis (elev. 1400 m).

7.13 Relation of magnitude of and drainage basin. 10.3 Fluvio-glacial material in the left Aiguamoix bank,

7.14 Reservoirs of the Upper Aiguamoix area. 700 m south from the dam.

7.15 of in 10.4 of the left Relation the inflow and storage the Upper Geological profile Aiguamoix bank at the

Aiguamoix area. damsite.

7.16 Flood routing through the Aiguamoix west branch. 10.5 Hydrogeological section along the Aiguamoix dam

8.1 Average monthly temperatures during the period axis.

1955—1965. 11.1 Structures of the Devonian limestones related to the

8.2 Average monthly wind velocity during the period Güells del Jueu system.

11.2 of 1955—1965. Outcrops karstified limestones, catchment areas of

8.3 Average monthly Penman-evaporation values and karst systems and surficial water divides in the Valle combined Penman-Dalton evaporation values. de Aran.

8.4 Monthly decrease in outer atmosphere shortwave 11.3 Two geological profiles of the Pila-karst system.

radiation and in the 11.4 of the Pila-karst (odHsh) on a valley bottom error Discharge measurement spring. monthly Penman evaporation values due to mountain 11.5 Map, showing the situation of the Güells del Jueu shadow (1965). karst spring.

8.5 11.6 Relation Shadowed areas in the Valle de Aran during the of the fast runoff and baseflow of the Güells

winter solstice at 12.00 h. del Jueu karst system.

11.7 Runoff 8.6 Relation of the percentage shadowed area during the analysis of three hydrographs of the Güells

winter solstice and the of 31 del karst average weighted slope Jueu system.

basins. 12.1 Graphical correlation of the runoff of the Pontet de 8.7 Comparison of calculated and measured shortwave Rius- and Aigiiestortes-basin. radiation (Hsh). 12.2 The "roche moutonnée" landscape in the Pontet de 3.8 Average height of the monthly 0°C-isotherm during Rius basin.

the period 1955—1965. 12.3 Hypsometric integrals for eight basins.

9.1 Position of the of the the 12.4 Runoff ofthe de Aran glaciers Aneto group during entire Valle during the calendar of 1958. 1956. summer year

TABLES

2.1 Specific degradation values of twelve rivers (mm/1000 6.7 Increase of the precipitation from the valley station

Arties to six mountain stations in m _1 _1 year). mm.100 .year .

2.2 Volume 3 of out of the Valle de (km ) rock, discharged 6.8 Average annualsnowfall (cm) for eleven stations during Aran during successive erosion phases. the period 1946—1966. 5.1 air in Arties Monthly average pressures (mb) (elev. Water of fresh 6.9 content snow (percentage), measured at 1138 and Viella (elev. 935 m) m). three stations during the period 1956—1966. 5.2 fluctuation in air Monthly average daily pressure (mb) 2 7.1 New drainage areas (km ) after the construction of for Arties (elev. 1138 m) from 1959—1965. hydropower systems. -1 5.3 wind in Restanca Monthly average velocity (m.s ) 7.2 Areas of units of the land classification for (km*) map during the period 1957—1965. thirty-three drainage basins. 5.4 Non ventilated relative air humidity values (percent) 7.3 Distribution of land classification units in the Pontet of Arties (08.00 h and 18.00 h) and Viella (08.00 h). de Rius basin. 6.1 Seasonal precipitation coefficients for five stations ( 1946 7.4 Distribution ofland c assification units in ten drainage —1966). basins of the Valle de Aran. 6.2 Fluctuations in the annual precipitation for five 7.5 fourteen in stations. Characteristics of lakes the Upper Aigua- moix 6.3 Frequency and humidity of winds (percentage). area.

8.1 Penman values the 6.4 Frequency of cloud cover (percentage) during dif- monthly evaporation (mm) during ferent winds. period 1955—1965.

6.5 Regression analysis of monthly precipitation values. 8.2 Comparison of Penman-, Penman-Dalton-, Thornth-

6.6 Average annual precipitation values (mm) during the waite-, and Turc-annual evaporation values (mm) period 1946—1966. during the period 1955 —1965. 4 H. Rijckborst: Hydrology of the Upper-Garonne basin

8.3 Short wave radiation measurements in Restanca and 9.3 Average monthly evaporation and sublimation values

Viella during 1965 with Gun Bellani pyranometers (mm) for the Aneto area.

2 1 cal. cm (in .day ). 11.1 in the karst systems. 8.4 Average monthly percentage of the Valle de Aran 11.2 Results ofcolor tracer experiments in the karst systems. covered with snow during the period 1955—1965. 8.5 Dalton values monthly evaporation (mm) from a snow 11.3 Chemical analyses of the Cambro-Ordovician- and

cover at Restanca and Bonaigua. Devonian limestones.

8.6 tx-values, estimated for the Valle de Aran. 12.1 Water balance of the Pontet de Rius- and Aigiiestortes- 9.1 snowfall the of Average monthly (cm) on glaciers the basin (1959—1963). Aneto the 1955 —1965. group during period 12.2 Ten of basins year water balance eight (1946—1956). 9.2 Estimated vertical monthly temperature gradients

and Water balance the de Aran of (°C/100 m) average monthly temperatures (°C) 12.3 of Valle 1956, 1957,

at an elevation of 3000 m. 1962 and 1963.

APPENDICES TABLES 1—45

1. Monthly precipitation (mm) at Cledes (st. 1) 27. Average monthly number of frost days, with minimum

below 0° C 2. Monthly precipitation (mm) at Viella (st. 2) temperatures (1955—1965) 3. Monthly precipitation (mm) at Arties (st. 3) 28. Average monthly number of ice days, with maximum

4. Puerto de 0°C Monthly precipitation (mm) at Bonaigua temperatures below (1955—1965)

(st. 4) 29. Average monthly number of precipitation days (1955— 5. Monthly precipitation (mm) at Benos (st. 5) 1965)

6. Monthly precipitation (mm) at Cámara Barrados (st. 6) 30. Average monthly number of snow days (1955—1965)

7. North 31. cloud in — Monthly precipitation (mm) at Tunnel Viella Average monthly cover percentage (1955 (st. 7) 1965) 8. Monthly precipitation (mm) at Restanca (st. 8) 32. Average monthly number of cloudless days (0—1/10)

9. Monthly precipitation (mm) at Cámara Arties (st. 9) 1955—1965

10. Monthly precipitation (mm) at Moncasau (st. 10) 33. Average monthly number ofclouded days (9/10—10/10)

11. Monthly snowfall (cm) at Cledes (st. 1) 1955—1965

12. Monthly snowfall (cm) at Viella (st. 2) 34. Average monthly number of clouded days (1/10—9/10)

13. Monthly snowfall (cm) at Arties (st. 3) 1955—1965

14. Monthly snowfall (cm) at Puerto de Bonaigua (st. 4) 35. Average monthly number of days with northern winds

15. Monthly snowfall (cm) at Benos (st. 5) (1955—1965)

16. Monthly snowfall (cm) at Cámara Barrados (st. 6) 36. Average monthly number of days with eastern winds

17. Monthly snowfall (cm) at Tunnel Viella North (st. 7) (1955—1965)

18. Monthly snowfall (cm) at Restanca (st. 8) 37. Average monthly number of days with southern winds 19. Monthly snowfall (cm) at Cámara Arties (st. 9) (1955—1965)

20. Monthly snowfall (cm) at Moncasau (st. 10) 38. Average monthly number of days with western winds 21. Monthly snowfall (cm) at Bossost (st. 11) (1955—1965)

22. in 39. with unknown wind Average monthly temperatures °C (1955—1965) Average monthly number of days

23. Average monthly maximum temperaturesin °C (1955— direction (1955—1965)

1965) 40. Average monthly wind velocity m/sec (1955—1965)

24. Average monthly minimumtemperature in °C (1955— 41. Average monthly runoff (mm) of the Iñola river (st. 6)

1965) 42. Average monthly runoff (mm) of the Barrados river — 25. Average monthly temperatureamplitudes in °C (1955 (st. 16)

1965) 43. Average monthly runoff (mm) ofthe Negroriver (st. 13)

26. Average monthly temperature gradients in °C/100 m 44. Average monthly runoff (mm) of the Garona de Ruda

(1955—1965) river (st. 2)

LIST OF SYMBOLS

Dimensions

-1 E from a wet cover 2 0 evaporation plant mm.day A area m Eq evaporation characteristic in Pen- A¡ cross section of horizontal layer m* 1 man's formula mm.day b duration of rainfall day

h water m horizontal distance from the stage height B¡! average h snow 0 original depth cm reservoir to bedrock m

Bi horizontaldistance from the H"a net radiation J.m« 2 average

ofthe horizon- H short wave radiation J-m* downstream exposure 8h

tal bedrock m H outer short wave radia- layer to oa 8 h atmosphere

2 thickness of the horizontal tion Di average J-m

layer m ht snow depth after the elapse of t days cm 1 coefficient E evaporation froma free water surface mm.day j storage day E actual -1 k¡ coefficient -1 ac evaporation mm.day permeability m.day List of symbols 5

L heat of -1.°C-1 latent vaporization J-kg u wind at 2 meter 2 velocity above

of level -1 L¡ length horizontal layer m ground m.s

of the curve — p slope stage-discharge z length m

1 P rainfall intensity mm.day Z¡ vertical distance of the centre of

wa of mb ofthe horizontal the p vapour pressure water at height z gravity layer to

bedrock impermeable m wa maximum of p ]ja vapour pressure water a actual evaporation coefficient —

at height z mb mb.°C_1 Y psychrometer constant 3 _1 runoff m .day q A slope of the temperature-vapour runoff 3 _1 Q, m .s air pressure curve at temperature at 3 _1 annual Q. . mean flood m .s 2 m 2 33 height mb.°C-' flow 3 _1 Q_t groundwater m .day í> head m 0 hydraulic

t time s or day of -3 p density water kg.m

ABBREVIATIONS

Cbf. Dcf, EF: Koppen classification of climates G.L.: ground level

MSL.: mean sea level 6 H. Rijckborst: Hydrology of the Upper-Garonne basin Introduction 7

1. INTRODUCTION

1.1 The project

This study of the hydrogeology of the Valle de Aran in the High Pyrenees of Spain is a continuation of the

geological work, which has been carried out under the guidance of Dr. L. U. de Sitter, professor in structural and applied geology at Leiden University.

This geological survey was started in 1952 and com- pleted in 1960 by Kleinsmiede. The hydrogeological project of the Valle de Aran started in July 1964 and the results of the work have been in this It is compiled comprehensive report. an appraisal of the hydrology of a drainage basin, of 572 kilometers. The basic covering an area square

data, hydrological techniques and results are dis-

cussed. Part of this work has been carried out by students as master in science thesis projects.

1.2 Acknowledgments

The assistance of the students A. J. Brugman, B. van

Hoorn, H. D. F. Leniger and D. A. Zeilmaker have been benificial for this very study. The Dr. numerous inspiring discussions with prof. L. U. de Sitter Leiden during my study at University,

are greatfully acknowledged. The assistance of Dr.

C. Voûte is also much appreciated. The active cooperation of the research department of the "Koninklijke Nederlandsche Heidemaatschappij"

is most sincerely appreciated. Especially the scientific

guidance of Dr. L. Wartena and Mr. A. D. Kusse

has been of value. great

Sincere appreciation is extendedto Mr. A. A. Ruiten- berg (M.Sc.) for his assistance in the preparation of Fig. 1.1 Location of the Valle de Aran. the English text of this thesis.

The of the Fuerzas Eléctricas de Cata- management luña for the of their gave readily permission use between and Spain (fig. 1.1). The valley is

archives. M. A. Wiirth (P.Eng.) director of the con- situated at lattitude 42° N and departure 1° east of structora Pirinaica S.A., has materially supported and distance of 180 km Greenwich, corresponding to a this Gomez Pena encouraged study. Messrs Rivera, from the and 150 km from the Deo, Colon, Vidal, Sanmarlí, Vila and Torrijos gave . The Garonne, which is one of the valuable information about the of the Valle hydrology important French Atlantic rivers, has its headwaters de Aran. in the Valle de Aran. Since the valley is the only Miss C. P. Roest skill in the drawing J. displayed great Spanish territory (since 1659) at the French side of of the enclosed land classification and Mr. F. J. map the Pyrenean water divide, this beautiful rich and Fritz expressed fine artistic ability in the preparation strategic area has been the object of numerous wars. of the plates. Miss T. W. Terpstra typed the manu- Three percent ofthe Spanish electric power production script. is generated in this valley ( 1964). Financial assistance field towards the expenses of the work received from the and was "Molengraaff-Fonds" 1.4 History of the Valle de Arán the "Ministerie van Onderwijs en Wetenschappen". The north Pyrenean valleys were populated in the Upper Paleolithicum (Pericot, 1934). Descendants of 1.3 Location these people continued to live there during the Neo-

The Valle de Aran (= valley of Aran) is a small lithicum (Campistol, 1960).

in the central and of the In the Roman the of the Civitas drainage area highest part era, valley was a part of Convenarum and Roman which Pyrenees. It has a range in altitude 3000 meters. (Lizop, 1931) a road,

The valley is located at the French side of the moun- connected (south France) with Portugal, led

tain chain and its southern limit coincides with the through the Valle de Aran. We still can find Roman

main water divide. Except for the Valle de Aran, the inscriptions in churches of some villages and until also east-west drainage divide constitutes the frontier recently in the two balnearios, which were built 8 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 1.2 The medieaval church of Bossost.

Fig. 1.3 Tombstone of an Aranese nobleman (church of

Las Bordas) 12th century. by the Romans around thermal springs. At about 410

A.C. the Roman empire disappeared and people of The in the have Roman the Valle de Aran returned to their isolated existence. young villages valley names formed of the while the others have ancient Celtic Since In the tenth century the valley part names. mediaeval have and duchy of French Commingues. In 1036 it turned to times, seven villages disappeared has been built. The with the Kingdom of Aragon. The church of Bossost (fig. only one new village villages Celtic situated the sunside of the 1.2) dates from this period. names are at slopes The French occupied the valley from 1283 until 1298 Garonne valley. and subsequently it was transferred to the kingdom of Mallorca. Since 1313 the Valle de Aran is defini- tively a Spanish outpost, and it has been frequently the and in attacked by French, finally 1950by a group of Spanish exiles. Fig. 1.3 shows a sculpture on a tombstone of an Aráñese nobleman.

Since about 1900 the Valle de Aran has been selected by tourist as the 'Spanish Switserland'. The valley forms of the Province of Lérida and it is now a part connected with the remainder of Spain through a five kilometer long tunnel (elev. 1450 m) under the main Bonai- water divide and along the Bonaigua pass. The inaccessible the gua pass (elev. 2072 m) is during winter because of snow. Before the Viella tunnel was

isolated in completed in 1948, the Valle de Aran was the winter of The half year from the rest Spain. name of Aran has been explained in different ways. Soler Santalo whereas Caro (1906) supposes a Basque origin, Baroja (1946), Cenac Moncaut (1873), and Moner de Sisear Celtic 1.4 Stream of the Garonne River. y (1898), emphasize a origin. Fig. system Introduction 9

1.5 Stream system

The valley constitutes about one percent of the total

drainage basin of the Garonne River, which covers about 53.000 km2 (fig. 1.4). The Garonne River in the

Valle de Aran has a length of 36 km, while the entire

river, from the Pyrenees to the Atlantic Ocean, is

360 km long. The Garonne has its headwaters in the

Valle de Aran on the slopes of the Cabeza des Portans

(elev. 2240 m) in a small karst spring (fig. 1.5). The

river, after leaving the Valle de Aran, flows generally

northwestward into France and via Toulouse and

Bordeaux into the Atlantic Ocean.

Fig. 1.5 The karst spring Güell del Garona where the

Garonne River originates.

2. MORPHOMETRY

curved because the channels 2.1 Morphometric data 2.3 are slightly parabolic

are deformed by scree and recent river erosion. The Hypsometric curves are required for a precipitation of area-altitude of basins of the analysis of the Valle de Aran. In this chapter, how- frequency thirty-three Valle de Aran (fig. 2.1) is irregular and partly coin- ever, they are used as morphometric data. The hypso- ciding with the denudation levels, which have been metric curve is a frequency curve of area/altitude described by authors (see Kleinsmiede, 1960). (Scheidegger, 1958). Hypsometric histograms of many In the entire Valle de four of low relief thirty-three drainage basins and of the entire Valle Aran, areas be The can distinguished by morphometric analysis as de Aran are plotted on linear paper in fig. 2.1. points that do not fit into the hypsometric curve (fig. hypsometric curve ofthe Valle de Aran has afterwards 2.2): been drawn on double logaritmic paper (fig. 2.2) because parabols show as straight lines and as Nye 1. From 3500—3100m

demonstrated: a cross section has (1965) parabolic 2. From 2800—2700 m smallest resistance for a Indeed, flowing valley glacier. 3. From 2500—2000 m

the ofthe Valle de Aran are glacial valleys step-shaped 4. From 1100— 900 m superpositions of two or three parabolic channels (fig. between 2500—2000 elevation be 2.3). Consequently, the hypsometric curves of glacial Only the area m can

of called a real level in the Valle de Aran. valleys show step shaped superpositions straight planation if The others show minor deviations from the lines, plotted on logarithmic paper. Valley steps are as hypso- clearly distinguishable (fig. 2.3). metric curve. The frequency of area versus altitude

In the Valle de Aran is be with the between a hypsometric curve essentially can compared average slope two because horizontal lines 2.2. The combination of both asymmetric, the area bound by contour on fig. and above the longest contour lines is smaller than the curves permits a description of the morphology of the Valle de Aran: underlying area. The lower parts of fig. 2.2 and fig. 10 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 2.1 Hypsometric histograms of thirty-three basins.

Fig. 2.2 Hypsometric histogram and slope-altitude distribution of the Valle de Aran. Morphometry 11

Fig. 2.3 Hypsometric histogram and slope-altitude distribution of the Jueu- and Aiguamoix-River.

The high and steep cirque landscape (elev. 3500—

2500 m) contains two areas of moderate relief. An

area of low relief is situated between altitudes 2500—

2000 which served of accumulation m, as an area snow

where numerous Pleistocene glaciers originated. They descended from this planation level into eight beauti-

ful valleys (elev. 2000—1100 m) which merge into main the Garonne valley (1100—563 m), which con-

tains the lowest area ofmoderaterelief(1100 —900 m).

2.2 Influence of basin morphology on hypsometric curves

For the determinationof low relief areas in the valley from the it hypsometric curves, was required to study the effect of the shape of drainage basins and of the sections valley cross on the curves. Three simplified

valley cross sections (parabolic-, V-shaped-, and ellip-

were tested for various of basin tic) , types shapes (fig.

2.4). Results are shown in fig. 2.5 for a rectangular,

an elliptic and a circular drainage basin. It can be

concluded, that parabolic valleys can be distinguished

as straight lines on logarithmic paper, independent of the basin shape. It is not possible to distinguish elliptic- from the V-shaped-valleys, although V-shaped types show The circular basins show Fig. 2.4 Maps ofthree simplified valley cross sections. steeper curves. steeper 12 H. Rijckborst: Hydrology of the Upper-Garonne basin

hypsometric curves than the elliptic or rectangular The degradation for the Pleistocene has been calculat- ideal ed be types. It should be emphasized, that the three to 100 mm/1000 year in the Valle de Aran. If

cross sections of fig. 2.4 are simplifications. continuous erosion is assumed during the Upper- of Valle de Aran channels Plioceneand All valleys the are parabolic Miocene, Quaternary (20 million years), of and therefore which started at the 2500 glacial origin, hypsometric curves m level, an average specific offer of plotted on logarithmic paper a possibility to degradation only 33 mm/1000 year is required to determine the four of low relief that reach the level. that areas as points present It can be concluded in into do not fit the hypsometric curve. Valley steps, gene al, erosion in the Valle de Aran during part of in the which are general situated below the 2200 m eleva- Tertiary was not great.

tion, can be mistaken for planation levels (fig. 2.3).

The low relief in — 2.4 type the Jueu glacial valley (1100 Hypsometric integral

900 m) was found, because the hypsometric curve Scheidegger (1958) advocates the use of the hypso-

does not to a basin. An correspond steep drainage metric integral curve in order to define drainage of similar relief Barrados- and area was found in the various In this thesis it used patterns at stages. was to Toran valley from 1100—900 m. calculate the mass, which has been discharged out of

2.3 Specific degradation

The basin be specific degradation of a drainage can defined of as the total mass, expressed in terms thick-

ness (in mm) of a sheet, distributed over the entire

basin, which is discharged out of a drainage basin in

thousand From the literature one years. (Water Supply Papers 1251, 1351, 1401, 1450, 1451, 1520 and 1547) specific degradation has been estimated for twenty-eight Atlantic slope basins in the U.S.A. be- lattitudes 38°—45° N. Those basins have tween areas, comparable to that of the Valle de Aran (572 km2).

Because of the short time-range of the data, no reliable results were obtained for a period of one thousand

years. In general, specific degradation during a flood is 20—1500 times thf annual average degradation.

The arithmetic mean of specific degradation values for basins twenty-eight was 110 mm/1000 year.

Recent measurements of the specific degradation of

the Garonne basin near Toulouse indicate values

150—200 mm/1000 year. Table 2.1 shows specific degradation values of twelve rivers.

Table 2.1. Specific degradation values of twelve rivers (mm/ 1000 year)

Specific Area River 2 degradation km

mm/1000 year

Rhone 64,700 265 Rhone 90,000 200

Po 70,000 480

Po 77,700 548

Rio Grande 77,700 25

Irrawaddy 323,000 451

Upper Ganges 370,000 486

Uruguay 388,400 22

Danube 606,000 59

Danube 829,000 59

Indus 940,000 225

Hwango 1,812,000 268

Nile 2,848,000 10

Mississippi 3,221,000 63 Fig. 2.5 Hypsometric histograms of three simplified valley Amazone 5,594,000 200—270 cross sections for a rectangular-, elliptic- and circular-

drainage basin. Morphometry 13

the Valle de Aran. Volumes were sediment of thickness of 120 measured computed by apply- an average m, as formula. the ing a trapezium Fig. 2.6 shows hypso- in the field.

3 metric integral for the area. A inass of 391 km has

been discharged out of the valley since Miocene time, 2.5 Erosion models

if the Miocene base level is assumed to be 2500 m. Four areas of low relief occur in the Valle de Aran.

This is equivalent to 35 of the block between If erosion is assumed the maximum percent to start at present

the elevations 2500 and 563 In order to an m. get elevation of 3500 m and continue the to to present idea, of what 391 km3 the volume of the represents, base level of 563 m, three erosion models can be Adour- piemont of the adjacent huge devised. Four "planation" phases, corresponding to the 3 River has been estimated to be only 94 km four areas of low reliefin the valley (see 2.1) and four from data of Taillefer (1951). An thickness average intermediate erosion phases are assumed:

of 60 m of the piemont has been used. Apparently the Adour-Lannemezan piemont, if compared with the 1. In model 1 the assumption has been made, that

material discharged out of the Valle de Aran, is very 75 percent of the available volume is removed

3 small indeed. With 391 km material derived from the during the four planation phases, whereas only 50

2 Valle de Aran, a large part (3,250 km ) of the entire percent during the four intermediate phases is

Garonne molasse basin could be covered with a removed.

2. In model 2 the assumption has been made, that in removed. both phases 50 percent is Model 1 and 2 discontinuous in represent a uplift eight steps.

3. Model 3 is a refinement of model 2, because it is

calculated for 100 meter intervals rather than for

the total interval during the erosion phase. This

model represents a continuous uplift in thirty-five

steps.

Table 2.2 and figure 2.7 show the results of the model

analysis. Two graphs (fig. 2.7) show the removed volume of base per 100 meter lowering the level, and

the accumulated volumes, which were eroded during

the eight erosion phases. Model 3 can probably be

applied to the Pyrenees. Some information about

specific degradation during the Tertiary should make

it possible to estimate the required time for each

erosion phase.

2.6 Origin of the Garonne River

studied Hercynian structures were to determine their effect the of the Garonne River. on present position relief above Fig. 2.8 shows the a horizontal plane,

which is at situated at elevation of 3000 present an m.

Data from the profiles and maps of Kleinsmiede

used. The structure-contour (1960) were map (fig. of the of the Devonian that the Bossost Fig. 2.6 Hypsometrie integral of the Valle de Aran, show- 2.8) top shows,

the volume of eroded material 100 altitude. dome and the late Carboniferous intrusions underlie ing per m

Table 2.2. Volume (km 3), discharged out of the Valle de Aran during successive erosion phases

3500— 3100— 2800— 2700— 2500— 2000— 1100— 900— Increase erosion

3100 2700 2000 1100 900 563 m 2800 m m 2500 m m m m m range

Number erosion 1 2 3 4 phase

172.031 114.182 99.495 90.939 212.440 130.082 71.452 67.185 Model 1

114.695 142.857 99.700 105.176 163.903 161.472 84.344 86.831 Model 2

228.097 112.762 56.541 111.776 239.535 190.586 11.421 7.175 Model 3 14 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 2.7 Results of the model analysis ofthe Valle de Arán.

high areas which both reached elevations of 6000 of the latter sediments, even if preservation in a fault It be concluded that the of the meters. can position zone is assumed. This erosion phase is partly respon-

3 Garonne River from Las Bordas to Salardu sible for the removal of a mass of 530 km which was appears , be controlled the situated above to by Hercynian structures. During the 3100 m level (fig. 2.8) and partly

3 the Cretaceous, a small of the axial zone of the for the removal of a mass of 567 km which was part , above level. Therefore the situated between the elevations 3100 and 2500 Pyrenees rose sea present m m. Garonne and its S-N which The of the River, certainly part crosses rest mass, which was not eroded during the the Bossost dome, is ofTertiary age. The fault pattern Permian- or Triassic-phase, has been removed during has not affected the position of the main rivers. Many the Tertiary, together with the Mesozoic sediments. tributaries, however, are situated along fault lines. Taillefer (1951) considers the Garonne River as one of

the oldest features of the because it follows Although it is not certain that the Garonne River is Pyrenees

along the northern border of the Pyrenees a fault zone partly a Permian or Triassic feature, an old erosion of phase is required to explain certain features in the pre-Miocene age.

Valle de Aran. In the Aiguamoix valley, at an eleva- — 2.7 The Miocene level tion a planation of 2000 m, patch of Triassic- (de Sitter, 1953a De Sitter and 1956b; Kleinsmiede, 1960) or Permian-sedimentary (1956-b), Jelgersma (1958) Kleinsmiede rock has been found. From the date the level of 2500—2000 (Mattauer, 1966) map (1960) planation m as and of Kleinsmiede profiles it can be concluded, that Upper-Miocene. By hypsometric analysis we could there has been an erosion phase before the deposition trace this level in each river of the Valle de Aran Morphometry 15

Structure-contour of the Devonian in the Valle de Arán. Fig. 2.8 map top

Fig. 2.9 Morphometric analysis of the Iñola basin, show- ing the dip of the Miocene planation level in the direction

2.10 Glaciation of of the present river. Fig. a Tertiary planation level. 16 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 2.11 Cross section of the Toran valley at the Lower Toran damsite.

Fig. 2.12 Cross section of the Toran valley at the Upper Toran damsite. Morphometry 17

2.13 Distribution of the 100 altitude in basins. Fig. weighted average slope per m ten drainage

(fig. 2.1). It can be concluded, that the planation level St. Gaudens (50 km). The glaciation of the Miocene constitutes the remains of Miocene which level rise which a landscape, planation gave to typical glaciers, showed a significant residual relief of at least 1000 flowed inall directions into the steep valleys (fig. 2.10). meters. The regional slope of the Miocene erosional Recent erosion has dissected the glacial valley bottoms, surface dips in the directionof the present rivers, for in- for instance in the Toran River (figs. 2.11 and 2.12).

stance in the Iñola River (fig. 2.9). A hypsometric anal- The obervations are derived from numerous FECSA

ysis by Liezenberg (1967) in the adjacent Capdella area drill hole data. Miocene main shows, that the water divide was situated the the main divide. 2.9 at same position as present water Slopes

Average slopes were determinedfor all drainage basins 2.8 Quaternary developments of the Valle de Aran in the Valle de Aran. The average slope was obtained the bstween successive After the hot and moist Miocene and the dry Pliocene by dividing area two contour

(Flohn, 1965 — Taillefer, 1951) cold and dry climates lines by the arithmetic mean of the length of those

contour lines. The relation of the followed in the Pyrenees (Fairbridge, 1965). Glaciers average slope to

descended into the Garonne altitude is in 2.13 for ten valley, and reached even cumulatively plotted fig. river basins. The of the entire average slope Valle de Aran is shown in fig. 2.2. The frequency of the

average slopes is shown in fig. 2.14. Slopes between 28° and 31° The of low relief are very frequent. areas

in the Valle de Aran are not apparent on fig. 2.13 because the elevation many steep slopes at same as the of areas low relief predominate. The regular increase

of drainage area in a downstream direction of the

Garonne River is shown in fig. 2.15.

Fig. 2.15 Length profiles of the Valle de Arán rivers and

increase of drainage area in a downstream direction of

2.14 of the Garonne River. Fig. Frequency weighted average slopes. 18 H. Rijckborst: Hydrology of the Upper-Garonne basin

3. AVAILABLE METEOROLOGICAL DATA

3.1 Introduction 3.2 Precipitation and snowfall

The three and The basin has been well temporary seven permanent meteoro- Upper-Garonne equipped stations in the Valle de Aran with 10 measured rain distrib- logical are managed by daily gauges. They are

basin of 2 the Spanish hydroelectrical company FECSA. The per- uted throughout the entire 572 km . In

stations situated addition to these 10 rain manent meteorological are at power gauges, accumulating gauges

stations while temporary posts are mostly situated of the Mougin type have been mounted high in the construction sites of the FECSA. mountains of the Valle de Aran. The near important Mougin gauges

FECSA has commenced with the recording of mete- are measured 1 —3 times a year. 3.1 the of the rain orological observations in 1946. All the available data In figure position 20 gauges is

over the period 1946—1966 were placed at our dis- indicated. In order to show the periods of precipitation

posal. The meteorological information is stored in the records the bar graph figure 3.2 has been drawn for

Viella head office. Except for the precipitation, all all gauges from 1946—1966.

other climatic elements have been analysed over the Data of self recording rain gauges are not available in period 1955—1965 using data from the Cledes, Viella, the Valle de Aran.

Arties, Restanca and Bonaigua meteorological stations. The 10 daily observed rain gauges have a height of

Fig. 3.1 Location of meteorological stations. Available meteorological data 19

minimum and actual in °C. These mum, temperature

variables are measured at a height of 1.50 m above

GL. Calibration of the Six-maximum-minimumther-

mometers used at the stations, showed small systemat-

ical errors for all thermometers.

at The daily wind direction a height of 3 m above GL

is registered at 08.00 h. as north, east, south or west. Wind force is estimated simultaneously and registered

as Fuerza (force) 1, 2, 3 and 4. Windforce estimations

can be converted to Beaufort with Fuerza n = Beau-

fort 2n. This equation has been derived from control

measurements in Restanca with a rotation anemo-

meter at 2.00 m above GL. Wind velocity is not

measured.

Cloud-cover is estimated every day at 08.00 h, which

are sometimes accompanied by a cloud description.

These cloud types are not defined according to W.M.O. standards (International Cloud Atlas). The Fig. 3.2 Bar graph, showing precipitation records from observed cloud types in the Valle de Aran data are 1946—1966. described in the Atlas reducido de nubes, publ. Cl2 (1943) of the Servicio Meteorológico Nacional de

España.

1.45 m above GL (ground level) and an orifice surface

2 are read at 08.00 h. of 200 cm . These gauges daily 3.4 Air pressure and air humidity All Mougin accumulating rain gauges have an orifice In the station Viella and Arties 2 power (1956 —1966) of 200 cm while their heights reach to 2.50 m above (1959—1966) the air is registered with baro- GL 4.40 above GL. In 3.3 the latter pressure or to m fig. type At the same stations air measure- 4.40 graphs. humidity of gauge is shown. Whether a height of 2.50 m or ments are carried out at 08.00 h and at 18.00 h using m is maintained, depends on the snow height at the ventilated dry and wet bulb psychrometers. The gauging site. After measuring the accumulated pre- air data have been available from Viella the is filled humidity cipitation in a Mougin gauge, apparatus since 1960 and in Arties since 1963. The air humidity again with 1 liter water, vaseline and calciumchloride. above measurements represent the situation at 1.50 m The CaCl attacks however the zinc anticongealing 2, GL, but they are not recorded during the winter time. catchment basin of the This results in Mougin gauge. losses of precipitated water during a period ofmeasure- which but difficult 3.5 Unused records ment, are not very frequent, to detect and to evaluate. Pre-1946 meteorological information from the mete- stations and also in Near the 10 meteorological Bossost, orological stations Cledes, Viella and Bonaigua have the GL is measured at 08.00 h. daily snowheight on not been analysed because they show interruptions and the of Most data include total snow height height during the Civil War and during World War II. For the fresh fallen snow level. de at ground our analysis of the climatology of the Valle Aran

the period 1946—1966 was the only one with continu- 3.3 wind direction, wind and cloud-cover with Temperature, velocity ous precipitation observations coinciding an

At the meteorological stations Cledes (650 m), Viella equal period of continuous hydrological records. The of Centro (932 m), Arties (1138 m), Restanca (1982 m) and old records are stored in the archives the Cataluña Servicio Mete- Bonaigua (2072 m) the temperature, wind direction, Excursionista de (Barcelona) ; Eléctricas wind force and cloud-cover are observed daily. orológico Nacional (Zaragoza) and Fuerzas

Temperature measurements at 08.00 h. include maxi- de Cataluña S.A. (Barcelona). 20 H. Rijckborst: Hydrology of the Upper-Garonne basin

rain Fig. 3.3 Mougin gauges. Climatology of the Valle de Aran 21

4. CLIMATOLOGY OF THE VALLE DE ARAN

4.1 Introduction from Restanca (1982 m) and Bonaigua (2072 m).

An evaluation of the climatic elements of the Valle de The Koppen classification can also be applied to the

Aran is essential for the determination of the terms highest peaks of the Valle de Aran which are situated

near the divide. Those evaporation and precipitation in the water balance. Pyrenean water high moun-

tains, from 2300 to 3400 have an EF For that purpose the meteorological data over the ranging m, climate with abundant annual period 1955—1965have been analysed for the stations precipitation ranging Cledes, Viella, Arties, Restanca and Bonaigua. The from 2000 mm to more than 3000 mm. The precipita- tion is distributed analysed data are summarized in tables 1—45. evenly in all seasons. The high peaks

above 3000 m are characterized nine frost months The Valle de Aran has an almost endless variety of by

local whereas three months have an climates, because it is a high mountain basin. average temperature than 0° C. It is difficult to give a complete idea of all those local higher

climates with the data from only five meteorological

stations distributed 2 of 572 km . The 4.3 The the Valle de Arán climate. over an area effect of Pyrenees on the atmospheric conditions in the Valle de Aran vary The Valle de Aran is situated at 180 km from the markedly with and rapidly with variations exposure Mediterranean Sea and at only 150 km from the in height. The climate of the broad Garonne is valley Atlantic Ocean (fig. 1.4).

different from that of an The very exposed high peak. The climates in the Valle de Aran in the centre of the climate of the windward slopes differs greatly from therefore influenced High Pyrenees are strongly by that of the leeward slopes, and the flanks inclined the presence of those extensive bodies of water. towards the sun are dissimilar from those which are The exceptional climate of the Pyrenees can be attri- shaded slopes. The 10 observation is years period buted to its peculiar geographic position: the East- statistically not long enough for an evaluation of a West direction of its the mountain chain and great certain climatic The type. description ofthe "climates" which exceeds the altitude of the altitude, average in the Valle de Aran is only based ten of upon years Alps by 100 meters (Dominy, 1965). Most of the continuous observations (1955 —1965), which is in- northern side of the Pyrenees contrasts sharply with sufficient to comply with the international accepted the dry Spanish side of the mountain chain, which is period of 30 (1930—1960). years strongly affected by the Iberian continent and the Mediterranean Sea.

4.2 Classification of the climates the Atlantic The climate of the western Pyrenees, near The classification of Koppen (1922) has been applied coast, is strongly influenced by the Atlantic Ocean the to meteorological data 1955—1965 of the Valle de and especially the Gulf Stream. The zone ofmaximum Aran. It has be that the border to emphasized Koppen precipitation near the maritime northwestern

classification to of the is situated low alti- attempts classify highland climates, western Pyrenees at a very the of climatic face of by employing same system types and tude. This zone rises along the northwestern their limiting boundaries as for a hypothetical conti- the mountain chain in an eastward direction until it nent of low and uniform elevation. reaches the Valle de Aran, which is situated in the

The classification the main Garonne Koppen gives central Pyrenees. Those central or high Pyrenees with the stations Cledes Viella consist of 220 km continuous of summits valley (650 m), (932 m) a long range and Arties Cbf climate. This that the (1138 m) a means exceeding 2500 m elevation. The passes across the broad Garonne is characterized mari- altitudes from 1600 valley by a high Pyrenees have ranging to time moderate climate with precipitation in all sea- 2300 m. In the intramontane Valle de Aran, in the

At least four months have of maximum sons. average temperatures centre of the high Pyrenees, the zone 10° C. the exceeding precipitation coincides with the highest peaks on The of the Valle de Aran from 2300 higher parts have a Dcf main water divide, which range in altitude

climate. This a mountain climate with the eastern eastward from implies pre- to 3400 m. In Pyrenees, in all In such climate diminishes due cipitation seasons. a two months Andorra, the precipitation greatly to have average temperatures higher than 10° C. the proximity of the Mediterranean Sea (Solé Sabaris The Dcf climate is determined by using the data 1962, Lautensach, 1964).

5. CLIMATIC ELEMENTS

5.1 Air pressure with the ideal vertical of 0.0065° temperature gradient In 5.1 the -1 figure mean monthly air of Arties "Cm but with the measured gradients of 0.0054° pressure ,

1 1 (1138 m) and Viella (932 m) is compared with the "Cm- (Viella) and 0.0053° Cm- (Arties). The ideal Naca standard for those Naca for Viella and atmospheric pressures two atmospheric pressures (906,2 mb.) stations. The Naca for be the atmosphere the two stations Arties (884,3 mb). appear to superior to meas- has been calculated according to the Smithsonian ured values. tables This meteorological (1951). has not been done In the same figure the summer air pressure increase, 22 H. Rijckborst: Hydrology of the Upper-Garonne basin

appears to be considerable; it is the greatest during the

winter time and the smallest in the summer months.

Table 5.1. air in Arties Monthly average pressures (mb) (elev.

1138 m) and Viella (elev. 935 m)

Viella Arties

mb mb

J 901.9 873.8 F 901.8 873.1

M 900.5 871.4

A 899.3 872.7

M 903.1 876.2

J 903.7 878.2

J 904.9 979.3 A 904.9 879.0 Fig. 5.1 Mean monthly air (mb) of Arties and pressure S 903.8 878.3 Viella, compared with the Naca standard atmosphere. O 902.1 875.4

N 899.0 872.1

due to the of the Azores shifting position high pressure D 893.4 870.5 ridge, is clearly demonstrated for both stations. The air for Arties and Viella monthly average pressures

are summarized in table 5.1. For the station Arties Year 901.5 875.0

the Naca 906.2 884.3 monthly average daily variation in air pressure has been determined (table 5.2). The daily variation

Table 5.2. in air Arties 1138 1959—1965. Monthly average daily fluctuation pressure (mb) for (elev. m) from

J F M A M J J A S O N D Year

2.8 2.8 3.2 2.4 2.0 2.0 2.0 2.4 2.0 2.0 2.8 2.8 2.4

5.2 Temperature the Garonne valley January is the coldest and driest

In the Valle de marked variations month ( —4° C), whereas for the mountain stations Aran, occur during is the coldest month. For all the various seasons. The daily air temperature fluc- February stations, July is the warmest which indicates the tuations at 1.50 m above GL are also considerable. month, strong

In 5.2 the of influence of the Atlantic Ocean. fig. mean monthly temperatures a typical The annual number of with valley station such as Viella (932 m) and of a typical days freezing temperatures mountain station in the Valle de Aran from 80 in the Garonne such as Bonaigua (2072 m) are ranges 200 the altitude of 2000 At the 3400 In the the valley to at m. m compared. same figure average monthly level this number increases to 360. as well as the absolute maximum- and minimum- probably

The data of the period 1955—1965 are temperatures are indicated. The figure shows that temperature compiled in 22—28. the average monthly amplitude in Viella amounts to appendix-tables 12° C, while the amplitude in Bonaigua is only 8° C. This is due the influence of the 5.3 Vertical gradients to more important temperature free at The In the between the atmosphere Bonaigua. monthly tempera- order to compare gradients ture fluctuations the than the annual fluctuations for are greater during summer meteorological stations, during the winter, in both Viella and Bonaigua. In the period 1955—1965 have been plotted in fig. 5.3. figure 5.2 it is shown that the difference between the Vertical gradients on the Garonne valley floor are warmest and coldest month is 15.6° C in Viella, extremely small, variable and in some months even whereas the in Bonaigua it has a value of 14.1° C. inversed. On steep valley slopes, however, tem- The annual for the Garonne be the Naca average temperature perature gradients can as high as gradient

valley has a high value of 10° C. The highland stations and they are constant throughout the year. The gra- the dients between the mountain stations on contrary have a low value of only 3° C. The two high are

coldest month is the for the Garonne and variable. vertical tem- not same valley extremely steep Very steep observed and the highland stations Restanca and Bonaigua. In perature gradients have also been between Climatic elements 23

of station Viella and the mountain station Fig. 5.2 Monthly temperature the valley Bonaigua.

and October November the lower of April to parts

the valleys are free of snow while the area at the 2000 the Valle de m elevation is deeply covered. In August Aran is free of whereas in December completely snow,

to January it is entirely covered.

5.4 Wind

The valley topography controls largely the movement terrain such of the air masses, in a steep mountainous

as the Valle de Aran, with a weighted average slope

of 27°. The rough valley topography and the slopes in the variation in wind directions. explain part great The results The latter are measured only at 08.00 h. therefore of the observations give very incomplete information about the daily mountain-valley air-

circulations. The wind roses from all meteorological

stations in the Valle de Aran show a maximumparallel

to the trend of the valleys (fig. 5.4).

A typical morning valley slope wind, observed in the of is drawn Valarties valley during the summer 1965, north-south oriented in fig. 5.5. In this case the valley

shows cold air flowing downside the shaded east slope

and rising warmer air on the sunny west slope.

Results of wind velocity measurements, with a rota- Fig. 5.3 Annual fluctuation of temperature gradients tion anemometer, showed that at Restanca the wind during the period 1955—1965. wind is in direction velocity is low when the blowing a

at right angles to the Valarties valley. Wind velocity Restanca Mar the when the wind is Lago and Lago during summer. appears to be higher blowing more Maximal vertical in the less the Valarties month- temperature gradients occur or parallel to valley. Average October velocities for listed in table 5.3 Valle de Aran from March to April and to ly wind Restanca are minimum be ob- From November, whereas gradients can for the period 1957—1965. May to October,

-1 served in December to and also in the wind is 3.8 m.s whereas from January August. average velocity , This is the absence of wind largely due to presence or snow November to April the average velocity has a in certain of the Valle de Aran. In March to value of 4.3 -1 parts m.s . 24 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 5.4 Wind roses from meteorological stations during the period 1955 —1965.

Table 5.3. wind 1 in Restanca the 1957—1965 Monthly average velocity (m.s- ) during period

J F M A M J J A S O N D Year

4.7 4.5 4.3 3.9 3.3 3.1 3.3 3.6 3.5 3.8 4.2 4.3 3.9

5.5 Cloud cover According to our observations (1965), cloud cover in The cloud cover varies little over the entire Valle de the Valle de Aran increased during the afternoon and Aran. The average annual percentage of clouded days reached a maximum at about 16.00 h. In the valleys,

amounts to 46 at all stations. April has the most cloud- radiation fog has often been observed in the early ed days (60 %) whereas January has the smallest morning and evening. Most cloudy days coincide with percentage (41 %). northerly winds. Persistant northern wind forces the

Cloudless the winter the water divide. A days are more frequent during fog up against high subsequent than during the summer months. Since cloud cover reversal from northern to southern wind results in a observations carried 08.00 of the clouds downstream. the are only out at h, daily rapid transport Near

variations are not recorded. high water divide, which forms the southern limit of Climatic elements 25

5.6 Relative air humidity

Measurements of air humidity are restricted to the

Viella-and Arties-meteorological stations. Dry- and

wet-bulb psychrometers at these stations are placed in ventilated GL. a housing at 1.50 m above During carried in the of 1965 measurements, out summer

(Brugman, 1965) it appeared that the non ventilated in Restanca psychrometer vapor pressure values (1982

m) had to be multiplied with a factor 0.75 in order to

obtain the right values at that station. The factor

0.75 be used the ventilated can to correct non vapor

pressure values of Arties ( 1138 m) as listed in table 5.4. In the the non-corrected same table, average

monthly relative air humidity values at Viella are Viella given. Relative air humidity data at seem more reliable than in Arties, because the Viella station is

better ventilated. Fig. 5.5 Morning valley slope wind in the Valarties valley. Relative air humidity in Restanca, with northern

wind, is about 30 percent higher than with other wind directions. difference between the Valle de Aran, the cloud cover appears to be In Arties, there is little slightly greater (about four percent) than in other the monthly average relative air humidity values

of the basin. measured at 08.00 h and those of 18.00 h parts (table 5.4).

Table 5.4. Non ventilated relative air humidity values (percentage) of Arties (08.00 h and 18.00 h) and Viella (08.00 h)

J F M A M J J A S O N D Year

Arties 75.2 75.2 79.3 80.9 79.7 83.0 81.9 81.5 78.2 78.5 76.8 75.9 78.8

08.00 h

Arties 74.1 74.7 80.4 81.0 81.2 83.4 80.7 80.9 77.1 80.3 70.0 77.0 78.4

18.00 h

Viella 72.4 55.9 52.2 54.9 59.6 65.3 64.0 62.2 58.6 63.3 63.3 53.3 60.4

08.00 h

6. PRECIPITATION ANALYSIS

6.1 Introduction between valley stations and mountain stations (Table

The mean annual precipitation in the Valle de Aran 45). In 6.1 it is that March, increases from nearly 900 mm in the lower Garonne fig. shown, January, February,

July and October are relatively drier months in the valley to more than 3000 mm on the highest peaks of Garonne valley. The mountain stations do not show the Maladetta massive. The weighted average of the the dry October month. Maximum precipitation for annual precipitation for the period 1946—1966 has a the stations falls in for the value of 1325 mm. valley December, except

mountain stations in Novembsr. The minimum The mean annual snowfall increases from 100 cm in pre- for all stations falls in the lower Garonne valley to more than 1000 cm in cipitation meteorological annual February. the Upper Esera valley. The weighted average The seasonal precipitation coefficients for the Garonne snowfall amounts to 503 cm for the period 1946—1966. stations Cledes Viella and This means that with a water content of 10 percent valley (650 m), (932 m) of fresh fallen the snowfall total Arties (1138 ) show only minor variations (table 6.1). the snow, average to The mountainstations Restanca and Bonai- precipitation ratio has a value of 0.38. (1982 m) have abundant gua (2072 ) autumn precipitation com- pared with the valley stations. The number of precipi- 6.2 for Precipitation regime tation days is about the same all months. The The in the Valle de Aran annual number of is 140 precipitation (1946—1966) average precipitation days

is evenly distributed throughout all seasons, but small days for five stations. This corresponds to eleven to variations evident. There be differences twelve are appear to monthly precipitation days (table 29). 26 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 6.1 Monthly precipitation coefficients for the valley stations and mountains stations.

Table 6.1. Seasonal precipitation coefficients for five stations (1946—1966)

Months Cledes Viella Arties Bonaigua Restanca

M, A, M 1.03 0.99 0.98 1.05 0.94

J, J, A 1.02 1.03 1.04 0.94 1.00

S, O, N 1.02 1.01 0.98 1.09 1.24

D,J, F 0.94 0.96 1.00 0.91 0.82

6.3 Variations in the annual precipitation 1946— 1966

The fluctuations in the annual precipitation for the same place the highest daily precipitation has been period 1946—1966 are not great. The ratios of maxi- measured on November 15th (176 mm). Both precipi- and minimum for tation melted mum precipitations 20 years are maxima were measured as snow. all smaller than 2.0, while the average deviationsof the Figure 6.2 shows the 19 maximum daily rain precipi- average annual precipitation have a maximum value tation values for Viella and Restanca. In the same of 15 duration lines of in percent (table 6.2). figure, (rain) precipitation periods

The highest monthly precipitation has been observed Viella and Restanca are indicated. Those lines are

in Restanca in October 1960 (657 mm), and at the important in the runoff studies and flood analyses.

Table 6.2. Fluctuations in the annual precipitation for five stations

Average Maximum Minimum Ratio of Ni—N Slation Altitude annual Years annual annual maximum 2 1 |

i =0 n precipitation precipitation precipitation minimum

Cledes 650 m 925 mm 1947—1966 1116 mm 694 mm 1.6 11%

897 635 1.8 Viella 932 m mm 1946—1966 1183 mm mm 13%

Arties 1138 m 937 mm 1947—1966 1273 mm 661 mm 1.9 15%

2072 1.5 Bonaigua m 1262 mm 1952—1966 1562 mm 1038 mm 10%

Restanca 1982 m 1720 mm 1956—1966 2347 mm 1217 mm 1.9 11% Precipitation analysis 27

Fig. 6.2 Maximum daily rain precipitation and rain duration for Viella and Restanca (1955—1965).

Table 6.3. Frequency and humidity of winds (percentage)

Wind direction Station

N E S W

Viella 27.2 37.6 33.2 2.0 frequency of winds (percentage) Restanca 25.2 13.5 60.5 0.5

39.8 23.2 1.2 of the Viella 35.8 percentage total precipitation

Restanca 29.8 18.3 51.6 0.3

1.8 of the Viella 36.7 42.2 19.3 percentage precipitation, 20 -1 Restanca 19.1 22.8 57.8 0.2 exceeding mm.day

Table 6.4. Frequency of cloud cover (percentage) during different winds

Wind direction Frequency of Percentage of days Station cloud cover

in cloud cover class N E S W class

Viella 64.4 35.6 24.6 24.3 9/10—10/10 37.0

Restanca 72.8 33.4 19.7 62.5 35.3

Viella 195. 21.3 22.4 25.7 1/10— 9/10 21.2

Restanca 16,4 28.2 56.9 25.0 22.7 Viella 26.1 43.1 53.0 50.0 0— 1/10 41.8

Restanca 9.2 37.7 56.9 12.5 42.0 28 H. Rijckborst: Hydrology of the Upper-Garonne basin

6.4 Relation wind direction and cloud winds of precipitation, cover predominate during all seasons (60.5 percent). southern 25—35 of the For the stations of Viella (932 m) and Restanca During winds, only percent while (1982 m), the relations of precipitation, wind direc- days are rainy, 53—57 percent are cloudless. and cloud for On the other hand 47—49 of the northern tion cover the period 1955—1965 are percent winds summarized in tables 6.3 and 6.4. bring rain and 84—91 percent of the days with northern winds clouded As could bs expected, moist northern and eastern are days.

of a of 20 mm winds bring most of the orographic precipitation and Important precipitation magnitude -1 day or more falls in Viella during eastern and north- clouds in the Garonne valley. This is evident during the winter when of the ern winds (79 percent) and in Restanca during south- (November-April), 58 percent ern and eastern winds (81 percent). northern winds bring rain or snow in Viella.

The "Balaguer", a local name for southern wind, is 6.5 The much drier in Viella all precipitation map in seasons, and it brings most Several involved in the of unclouded days. Only 25 percent of the days with problems were preparation the Valle de Aran southern wind brings rain in Viella. precipitation map (fig. 6.3).

At Restanca which is situated at 2 km The in (1982 m), only a. systematic errors the precipitation measure-

from the main water the relations of in mountainous the divide, precipita- ments a steep terrain, due to wind direction and cloud tion, cover are essentially height of the rain gauge orifices above ground level the in Viella. in Restanca southern and due the location of same as However, to the gauge.

6.3 of the Arán Fig. Precipitation map Valle de (1946—1966). Precipitation analysis 29

b. The influence of the major and minor topographical

features on the precipitation pattern.

c. The augmentation of precipitation data of six short

period stations with the data of four index stations

by means of a correlation technique.

6.6 Height of the rain gauge orifice

be From the literature there appears to overwhelming evidence that the influence of the height of the rain

gauge orifice on the results of precipitation measure-

ments is considerable (Braat, 1945 — Bleasdale, 1959

— Bruce & Potter, 1957 — Colenbrander, 1965 — - - - Gold, 1931 Haver, 1951 - - Kurtyka, 1953 — — Lacy, 1951 Nagel, 1954 Poncelet, 1959 — Ries-

bol, 1940 — Stanhill, 1958 — Winter, 1962).

In the Valle de Aran, all daily rain gauges have their orifices while the at a height of 1.45 m above GL, rain their orifices accumulating Mougin gauges have

at a height of 2.50 m or 4.40 m above GL. All these be precipitation measurements are lower than could

from with orifices situated at expected gauges ground level. This can be illustrated with some examples: Fig. 6.5 Accumulated precipitation values of Bonaigua,

a. At the station meteorological Bonaigua (2072 m), showing the 44 percent error in the measurements at 4.40

two rain are situated 10 m The lower m above gauges apart. ground level. rain above daily gauge (X) with its orifice at 1.50 m GL receives the 44 percent more precipitation than with its orifice 4.40 above Mougin gauge (Y) at m GL.

The equation of the line, drawn through the accumu-

lated precipitations of X and Y is: X = 1.39 . Y +

470 mm (fig. 6.4). The relation of X and Y is not in linear; the winter half year the difference between X and Y is than in greater the summer half year. This

is shown in fig. 6.5, where the broken line S (X—Y)

has been plotted for the period 1953—1961. The wind

effects on snow precipitation measurements with a

are more than rain Mougin gauge important on

precipitation measurements.

b. In Colomés (2170 m) in the high , Aiguamoix valley,

the Mougin precipitation, measured at 4.40 m above

GL, is 45 percent less than the precipitation, measured

at 1.45 in Moncasau m, (2017 m), although the is situated Mougin gauge 150 m higher above MSL.

The horizontal distance between Colomés and Mon-

is measurements casau two km and the were taken

over a five-year period.

c. In Restanca (1982 m) and Lago Mar (2230 m),

simultaneous precipitation measurements have been carried of the Mar out as part Lago project (Martinec,

Wartena, Brugman & Zeilmaker — 1966). The rain Restanca has of 1.45 gauge at a height m, whereas the Mar 0.40 above GL. Lago gauge was placed at m The horizontal distance between Restanca and Lago Mar

is one km and the measurements were taken over a

two month's period. The results indicate, that the

observed daily precipitation near Lago Mar in the 77 0.40 m gauge was percent too high, compared with the measured Restanca. 6.4 Double of daily precipitation near Fig. mass curve the Bonaigua precipitation

measured in and in rain A correction factor of which has been found at a Mougin gauge (y) a daily 1.44,

gauge (x). Bonaigua (2072 m), has been used to correct the 30 H. Rijckborst: Hydrology of the Upper-Garonne basin

results of the precipitation measurements for other applying the regression and correlation analysis the

with their orifices 4.40 above GL. were made: Mougin gauges at m following assumptions

In this manner the precipitation values at Saburedo 1. The monthly precipitations are normally distrib- (2330 m), Colomés (2170 m), Maladetta (2980 m), uted. Renclusa (2150 m), Pas Estret (2050 m) and Pia de 2. A stable precipitation regime is known to exist so l'Ana (1800 m) have been multiplied with 1.44. that significant correlation between the index For the Mougin gauges with their orifices at 2.50 m stations and the Yi stations be above GL different correction factors have been (Xi) can expected. estimated. For Mar correction factor 3. The rain localities and methods of Lago (2300 m) a gauge measure- of 1.10 has been assumed and for Artiga de Lin (1450 ment have not been altered.

a factor of 1.05. At Artiga de Lin the snow period m) 4. Xi and Yi are linearly related. is short. No correction has been applied for the Bausen

because the values With the IBM ofthe"RAET" gauge, precipitation correspond 1620 computer computer with the values of Cledes. centre of the Netherlands Land Development Con- Simultaneous taken at 1.45 snow measurements were sultants Ltd, Arnhem, 16 regression coefficients of Yi m above G.L. and at G.L. The latter reading average on Xi and of Xi on Yi have been calculated for the exceeds the former six by percent (6.12). monthly precipitation values. The correlation coeffi-

cients and standard deviations have been computed. 6.7 Regression analysis The results of the computations are listed in table 6.5.

The supplementary data from the index stations (Xi) After testing the correlation coefficients, all values be We therefore Cledes, Viella, Arties and Bonaigua have been used appeared to highly significant. can

better estimate of the conclude that thereexists a linear between to provide a population para- relationship meters of the (Yi) stations Beños, Camara-Barrados, the monthly precipitations measured in the Valle de

Viella Tunnel North, Cámara Arties, Restanca and Aran at various meteorological stations. This is in

Moncasau, whose records are shorter (fig. 3.2). By accordance with the results of Rubinstein (1956).

Table 6.5. Regression analysis of monthlyprecipitation values

Standard Correlation Correlatioi equations Index Altitude Station Number deviations (mm) coefficient

station of

items

Xi G r x¡ = Yl = (m) Yi x Gy

650 124 20.3 15.7 0.88 7.33 Cledes Benos 0.96y + 0.80x + 11.35

Cledes 650 Viella 232 25.2 23.4 0.82 0.88y + 11.11 0.76x + 16.05

Cledes 650 Cámara 68 20.5 21.9 0.87 0.78y + 2.84 0.97x + 20.43

Barrados

la 20.8 0.84 10.69 0.79x 13.19 Viel 932 Benos 124 22.0 0.90y + +

Viella 932 Cámara 68 19.9 24.1 0.85 0.70y + 9.69 1.03x + 15.91

Barrados

Viella 932 Viella 69 24.9 47.4 0.77 0.41y + 27.53 1.47x+ 9.08

Tunnel

North

Viella 932 Viella 68 21.8 31.7 0.82 0.57y + 9.67 1.20x + 25.44

Tunnel

North*

Arties 1138 Cámara 45 20.4 20.0 0.86 0.88y + 2.09 0.85x + 17.71

Arties

Arties 1138 Viella 232 21.4 20.6 0.86 0.90y + 9.8 0.83x + 10.70

Arties 1138 Restanca 126 29.0 66.8 0.69 0.30y + 35.50 1.60x + 15.14

Arties 1138 Restanca** 124 27.3 49.3 0.72 0.40y + 22.83 1.31x + 31.07

Arties 1138 Moncasau 70 25.4 44.2 0.75 0.43y + 20.65 1.31x + 24.41

Arties 1138 Bonaigua 176 29.3 36.0 0.72 0.58y + 16.36 0.89x + 36.55

Bonaigua 2072 Cámara 45 30.6 23.9 0.80 1.02y + 21.85 0.62x + 14.90

Arties

Bonaigua 2072 Moncasau 70 37.9 44.8 0.74 0.63y + 32.76 0.88x + 23.70

Bonaigua 2072 Restanca 126 37.4 66.1 0.70 0.40y + 52.14 1.24x + 6.03

* September 1960 not included.

** October 1960 and November 1963 not included. Precipitation analysis 31

Table 6.6. Average annual precipitation values (mm) during the period 1946— 1966

Meteorological Altitude Precipitation Mougin rain Altitude Precipitation

station (m) (mm) gauge (m) (mm)

Cledes 650 925 Pas Estret 2050 1415

Viella 932 898 Pia de l'Ana 1800 1350

Arties 1138 936 Saburedo 2330 1598

Bonaigua 2972 1255 Colomes 2170 1620 Benos 811 886 Artiga de Lin 1450 1355

Cámara Barrados 1280 1131 Renclusa 2150 1925

Viella Tunnel North 1400 1381 Maladeta 2980 2500

Restanca 1982 1607 Lago Mar 2300 1950 Cámara Arties 1940 998 Bausen 650 910

Moncasau 2017 1517

The regression equations of table 6.5 have been used Table 6.7. Increase of the precipitation from the valley station

Arties to six mountain stations in 100 1. to compute the mean monthly precipitations over the mm. m- 1 periods without data for the Yi stations. By applying year-

ten this procedure complete data of stations were

obtained for of Increase the preparation the precipitation map.

_1 Stations in mm. 100 m Direction The records from the . Mougin gauge ten high moun- tain stations 1 showed gaps. They have been calculated year- by applying the normal ratio method of the U.S.

Weather Bureau (1952). Arties—Bonaigua 34 ESE The results of all computations are given in table 6.6 Arties— Bonaigua, 52 ESE and these data were used in constructing the precipita- corrected tion of map the Valle de Aran. Arties—Saburedo 54 SE

Arties—Colomes 66 SSE 6.8 which Major topographie features, influence precipitation Arties—Moncasau 69 SSE

The Valle of Arties—Restanca 79 S de Aran has a weighted average slope

Arties—Lago Mar 88 SSW 27°, which has an important effect on the movement and stability of the flowing air masses. The air flow in the Valle de Aran moves in the broad and slightly curved Garonne valley and in its nine tributaries. The to Mar (2300 an increase of 110 which affect Lago m), however, watersheds, the precipitation pattern and 100 -1 has been observed. Therefore in mm . m^.year the air flow are indicated in figure 6.3 and 5.4. Garonne uniform the main valley a very precipitation The orographic precipitation in the Valle de Aran pattern exists; the situation changes completely near is largely induced by the air circulation from northern the main water divide. From table 6.7 it directions. Humid Atlantic air which the appears, masses, cross that the increase in annual precipitation from the Valle de Aran in a NW-SE direction, flow through station Arties is largest in a N-S direction (orographic the broad Garonne valley. The air flow is obstructed rainfall) and smallest in an E-W direction. Besides by the EW directed watershedof the Toran and Barra- the precipitation pattern in the N-S valleys, diverging dos valleys. The continuing air flow, funneling through exists in the E-W valleys of the Toran and the pattern seven NS directed valleys, is blocked at the high Barrados rivers, because frequent western winds from and Near the main narrow upper stream valleys. water the broad adjacent valley produce orographic divide, air masses are forced to rise over a continuous

precipitation on the slopes of the Liât mountains. EW of mountain which in altitude range peaks, vary from 2300—3400 meters which produces heavy oro-

6.9 Precipitation on valley slopes graphic rainfall (fig. 5.4). steep The relation of the annual precipitation and altitude For the study of the influence of minor topographical is shown The im- i.e. used the from in figure 6.6 for nineteen stations. features, steep valley slopes, we data portant increase of the precipitation with height three stations: Arties (1138 m), Cámara Arties (1940 and cannot without further data be applied to the area. m) Bonaigua (2072 m).

In the Garonne for decrease of 10 Cámara Arties is situated at the of the south valley instance, a top

-1 Garonne above the index mm . 100 m^.year in annual precipitation from valley slope, directly station

Cledes (650 m) to Viella (1138 m) has been measured, Arties. Arties is a valley floor station with an average annual of 936 The which is the result of the broad valley near precipitation mm. average annual Viella. in Cámara Arties 998 In the high mountains from Restanca (1982 m) precipitation amounts to mm. 32 H. Rijckborst: Hydrology of the Upper-Garonne basin

Relation ofthe annual and the Fig. 6.6 average precipitation (mm) altitude (m) during period 1946—1966. Precipitation analysis 33

Arties In spite of its greater altitude (802 m), Cámara

has only 62 mm more rainfall than Arties, corre-

-1 _1 an sponding with increase of 8 mm. 100 m .year . in the Garonne The increase precipitation on steep

valley slope is apparently excessively small. It can

therefore he concluded, that the precipitation pattern

in the Garonne valley is very uniform. This is also demonstrated by the extremely small increase from

Cledes (650 m) to Arties ( 1138 m), amounting to 5 mm

- 1 -1 100 m .year over a distance of 25 km along the Garonne valley bottom.

The second possibility to study the problem is offered of the Arties index by a comparison and Bonaigua stations. Despite the high elevation of Bonaigua (2072

m), its annual precipitation is low (1254 mm). The

increase in precipitation has a value of only 34 mm

_1 _1 100 .year . In order to correct the low value of 34

-1 -1 mm 100 m we have used the .year , computed

factor of Arties-Camara to Arties (8 mm 100 m~*.

1 year - ) for the valley slope near Bonaigua. The annual precipitation for the Garonne valley floor has been

calculated to be 1225 mm, by adjusting the 1254 This mm-value for Bonaigua. value gives us a "correct- ed Arties-Bonaigua factor", which corresponds with of an increase in average annual precipitation 52 mm

_1 1 100 m This value fits much better in the .year~ .

general precipitation pattern of the N-S valleys and in the general trend of table 6.7.

During the preparation of the precipitation map for 6.7 Relation of the annual snowfall and Fig. average (cm) the Valle de Aran we allowed for valley wall- and altitude (m) during the period 1946—1966. orographic-effects. The precipitation map for the Toran valley (fig. 6.3) is only approximate. stations is given in table 6.8. The relation of snowfall

and altitude is shown in fig. 6.7. 6.10 Snowfall The snowfall increases linearly with altitude and it is A snowfall the of eleven has map, using data stations, quite independent of valley effects. The valley effect been prepared. The snowfall data are listed in the from Cledes to Viella is only minor with a snowfall tables 11 —20 and 30. appendix, _1 _1 of only 23 cm.100 m .year while the average The normal ratio (method U.S. Weather Bureau) has > is increase in other parts of the Valle de Aran 50 cm. been determined for a number of stations and it has 100 m-^year- 1. been used the short observations. to complete range On the snowfall map (fig. 6.8) the linesof equal snow The average annual snowfall for each of the eleven height follow the contours of the topographical map.

The has been corrected for wind because map effects, Table 6.8. annual eleven stations walls de- Average snowfall (cm) for on steep cirque no important snow

during the period 1946— 1966 position is possible. The steep cirque ridges in the Valle therefore indicated snowfall de Aran are on the map of From the snowfall and as areas non deposition. map Meteorological Altitude Snowfall total the precipitation map a snow versus precipitation Station (m) (cm) ratio has been for the 1946— map prepared period 1966 (fig. 6.9).

Circles 650 58

Bossost 780 76 6.11 Snow duration

Benos 811 90 In the lower parts of the Valle de Aran the average 932 113 Viella is than 0° C winter temperature more (appendix- 1138 175 Arties snowfall short and tables 22—24). Periods of are Cámara Barrados 1280 256 irregularly distributed throughout the winter in the Viella Tunnel North 1400 252 Garonne The the Cámara Arties 1940 606 valley. average temperature during winter half in Restanca and how- Restanca 1982 575 year Bonaigua is,

Moncasau 2017 650 ever, always below 0° C. From the average tempera-

674 of winter half Restanca —2.1 Bonaigua 2072 ture the year at ( C)

and Bonaigua ( —2.7° C) and from the average tem- 34 H. Rijckborst: Hydrology of the Upper-Garonne basin

6.8 Snowfall of the Valle de Arán the 1946—1966. Fig. map during period

Arties-Restanca 1 the Valle de Aran is situated above the 1700 perature gradients (0.70° C.IOO m" ) m con-

-1 and Arties-Bonaigua (0.73° C.IOO m ), it is possible tour, the Upper Garonne basin has a tremendous calculate the half 3 to elevation of the winter 0° C isotherm. water storage in the winter year (140.10* m ), In the winter half the 0° C isotherm 18 of the total annual year appears to equivalent to percent precipi- be situated at the 1700 m level, which corresponds tation. with the Since 400 cm snow contour. 60 percent of

Table 6.9. Water content measured at three stations the 1956— 1965 of fresh snow, (percentage) during period

Total precipitation Number Total Water of snow depth at content % station in rain Meteorological gauge (mm) measurements G.L. (cm) of fresh snow at 1.45 above G.L.

Arties 282 1,945 1,831 9.4 Restanca 661 6,366 6,232 9.8

Bonaigua 724 7,583 6,863 9.1

Total 1,667 15,894 14,926 9.4 Precipitation analysis 35

6.9 Snow ratio of the de Arán the 1946—1966. Fig. to total precipitation map Valle during period

6.12 Water content offresh snow From 1667 measurements the water content average of fresh offresh fallen could be determined 9.4 It was possible to calculate the water content snow as percent.

snow by comparing the measured snow height at Meinzer (1942), however, measured a water content in the rain of 10.0 Our results show 6 lower ground level with the snow precipitation percent. a percent

gauges in the Valle de Aran. The results of the com- precipitation at a level of 1.45 m, compared with the

putations are listed in table 6.9. precipitation of snow at ground level.

7. RUNOFF

7.1 Introduction 7.2 Available data

The purpose of this investigation was to apply the Some ofthe thirty-three runoff gauging stations in the

of De mountainterrain Valle de Aran and built 1922 theory Jager (1965) on a steep were designed as early as as the Valle de Aran. The influence of vegetation, by the excellent Swiss engineer M. Würth. The entire

geology and morphology on runoff was also involved distributionpattern of the streamflow stages, weirs and in this the flood and the is the result of his study. Finally frequency recording gauges largely early and effect of hydroelectric power generation on floods was accurate studies concerning the hydrology ofthe Valle investigated. de Aran. Many old data, however, have been lost 36 H. Rijckborst: Hydrology of the Upper-Garonne basin

7.1 Distribution of runoff stations and catchment the effect of karst Fig. gauging areas, showing systems,

the Civil War and World War II. 7.1 three read and during Figure once a day, are once every three days, shows the distribution of the gauging stations, their two every fourteen days.

catchment areas and the influence of the karst on some The errors in the total annual discharge calculations,

drainage basin areas. Figure 7.1 represents the situa- produced by this method of reading the stream flow tion before the construction be estimated. of hydro power systems. stages cannot Continuous recorded

In the bar graph of fig. 7.2 the available surface water streamflow data over a restricted period were avail- data for 1945—1966 are shown, whereas in table 7.1 able from the stations 3,20 and 25. The data ofstations

the after the construction of 3 and 20 have been therunoff new drainage areas hydro used to compute charac- indicated. teristics ofthe and Valarties-rivers. power systems are Upper Aiguamoix-

The The data of station 25 used in the daily stage data of the runoff gauging stations were computations of karst reservoir proved to be almost useless in analyzing the fast runoff the of the Giiells del Jueu system

characteristics of the catchment areas, because they (see 11.10). read few are only once a day. Only a gauging stations 7.3 relations are equipped with concrete weirs, which give reliable Stage-discharge

data for the flood well for frequency analysis, as as It is common practice in the FECSA, to determine the

the calculation of the slow runoff characteristics or stage-discharge relations by measuring the water for the waterbalance. Almost all data could be used while velocity, the corresponding stage heights for the determinationof the runoff regimes. are read once or twice a month. Those measured

Of the runoff stations twenty-six twenty-one are read values are plotted for a calendar year on linear paper. Runoff 37

Fig. 7.2 Bar graph, showing runoff records during the period 1946—1966.

2 Table 7.1. New the construction order data into data. drainage areas (km ) after of to convert daily stage discharge hydropower systems It is evident that this procedure is inefficient. The

calculated errors in the total annual discharge, produc-

Runoff ed by this method, range from ten to twenty percent. Adjusted In order obtain better gauging Date of Hydropower to stage-discharge relations, a area station adjustment system constant slope of the water surface was assumed and (km 2 ) number the formula of Krayenhoff van de Leur (1965) was applied:

2 = h of log Q, p log + constant (1) (see list symbols). 2 42.3 19-12-'54 Arties I

2 0.07 8-'65 Arties II 26- The available stage-discharge data were divided into

3 6.10 19-12-'54 Arties I stage-discharge curves from June to May (fig. 7.3). 4 20.4 19-12-'54 Arties I The following errors could not be eliminated: the 5 2.6 26-12-'65 Arties II tremendous snowmelt runoff in spring, the variable 6 7.0 26-12-'65 Arties II backwater, the aquatic vegetation, and the ice or 7 112.7 19-12-'54 Arties I variable channel storage. 7 23.7 26- 8-'65 Arties II From 7.3 be obtained 8 32.3 19-12-'54 Arties I figure an impression can on how channels in the of 8 21.8 26- 8-'65 Arties II some change course two or

9 3.7 19-12-'54 Arties I three years.

14a 55.8 19- 3-'47 Viella

15 0.05 13-10-'56 Benos II 7.4 Land classification map and morphometric analysis 16 18.5 13-10-'56 Benos II The enclosed land classification map (scale 1:50.000) 17 19.6 28- 4-'58 Benos III was prepared by B. van Hoorn and H. Rijckborst 17a 8.9 12- l-'52 Benos I from sixty-two aerial X 24 20 6.1 19-12-'54 Arties photographs (24 cm)

27 16.6 13- l-'63 Toran — 1:37.000 — from 1948, covering the Valle de Aran

and the Upper Pallaresa. The total areas of the dis-

units such barren rocks tinguished as scree, etc. were

The obtained relation between and measured for each of the stage discharge thirty-three drainage areas. is used the FECSA for in (h/QJ by a calendar year The average error in the measurements amounted to 38 H. Rijckborst: Hydrology of the Upper-Garonne basin

7.3 Fig. Stage-discharge curves for runoff gauging station 13 (Negro River) and 16 (Barrados River).

six The results of the percent. computations are listed 2.1). The accuracy ofthose measurements was within in table 7.2 and 7.6. fig. five percent, largely due to the good quality of the The involved morphometric analysis the measurement topographical map 1:50.000 of the Valle de Aran, of the area-altitude distributions for each of the FECSA. prepared by This topographical map was thirty-three drainage areas (fig. The also used for the land classification The work 2.1). weighted map. of for each basin also determined average slope was (fig. the Swiss engineer W. Würth, who prepared excellent Runoff 39

2 basins Table 7.2. Areas (km ) of units of the land classfication map for thirty-three drainage

d Barren 'I Grass and £> rocks and Deciduous scattered «M O Barren scattered Arable Scree Grassland Lake Village trees and Conifers small rocks small land brushwood groups groups E of trees 1 of trees

1 1.62 4.05 6.81 0.50 2.72 0.52

2 6.49 11.76 2.34 0.25 — — 1.00 5.71 3.07 —

3 2.33 1.25 12.26 1.36 — — 1.70 0.41 1.23 —

— 4 1.86 4.25 0.03 — — — 1.45 6.76 0.70

5 3.23 18.15 4.51 — 0.05 0.13 — 0.52 0.52 0.37

6 0.53 3.22 0.04 — 0.06 — — 0.16 0.35 0.09

— 7 2.35 10.97 1.08 — 0.45 — 3.12 0.69 0.62

8 4.35 2.21 0.95 — 0.01 — 8.95 5.07 1.80 —

— 0.83 — 9 2.07 — 5.08 0.70 — — —

— — — — 10 0.79 — 4.32 0.53 0.06 0.27

0.82 — 11 0.91 0.21 1.82 0.30 — — — 0.57

12 5.17 13.85 1.63 — — 0.48 2.15 0.35 1.13 —

— 13 1.05 4.93 — — 0.03 0.50 2.25 0.10 0.90

14 4.35 15.01 1.56 0.07 0.50 1.10 3.65 1.66 0.55 4.35

15 4.13 17.20 5.82 0.19 0.04 1.05 2.22 1.67 0.45 —

16 1.05 4.32 0.07 — 0.06 2.20 2.85 1.66 — 0.22

— 17 1.02 7.20 0.25 — 0.10 2.78 6.00 0.15 0.23

18 0.80 7.46 0.03 0.04 0.17 1.62 3.35 1.40 1.00 0.10

19 2.59 9.53 2.30 — — — 3.71 0.57 0.92 0.35

20 1.21 0.44 0.90 0.90 — — 0.30 — 1.26 —

— — 22 0.12 0.94 0.21 — — 1.40 1.18 1.27

23 1.30 2.62 0.50 0.04 — 0.08 0.20 — — —

— — 24 0.39 2.90 — 0.01 0.90 1.40 0.07 —

— — — 25 1.59 4.77 2.59 0.06 — 1.10 0.54

26 1.65 12.43 0.37 — 0.93 8.63 19.90 7.70 — 9.15

— 27 0.03 7,20 0.15 — 0.03 1.24 1.17 0.70 0.27 28 5.00 12.62 4.85 0.29 0.46 7.78 9,40 4.32 3.10 1.25

29 0.62 1.23 0.72 — 0.32 3.46 2.90 8.76 0.80 2.10

30 0.20 1.67 — — 0.08 2.82 2.35 1.35 — 0.20

— 31 5.34 6.93 13.10 0.20 — — 0.02 4.97 0.90

— 32 0.67 2.11 0.85 0.05 — — — — —

33 1.82 4.51 4.11 0.40 — — — — — —

To-

tal 68.32 196.53 84.91 5.97 3.30 37.27 80.05 57.59 21.32 19.58

11.9 34.2 14.8 1.0 0.6 6.5 13.9 10.0 3.7 3.4 /o

at scale of 1:20.000 for the The of the flow is topographical maps a high theory fluctuating groundwater described and inaccessible parts of the Valle de Aran, deserves by Krayenhoff van de Leur (1958—1962), special attention. De Jager (1965), Martinec, Wartena, Zeilmaker &

Brugman (1966) and De Zeeuw (1966). According characteristics this the runoff characteristic of certain 7.5 Introduction to runoff to theory, a

catchment area comprises: The translation and transformationof a precipitation pattern into a runoff surge depends on the temporal 1. Percentage of the area contributing to a fast runoff. water The runoff in this is storage. intensity process determined mainly by the rainfall intensity P during 2. Thereservoir coefficient (j-value) ofthat fast runoff. runoff from A be calculated a time b; the q an area can 3. The base flow or the reservoir coefficient (j-value) for time t> b with the formula: of the slow runoff.

8 n2 WJ ) -n't/j M . da V -lí ~PA S = — q = -.e e (2) For example: 20% j 3.0 4 hours and 80% 71 n < ' n= 5... 1, = — 3, j 90.0 4 hours means, that during a short period

20 of contributes fast runoffwith = (see list of symbols) % an area to a j 40 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 7.4 Area-altitude distribution and hypsometric integral of the Pontet de Rius- and Aigüestortes basins.

Fig. 7.5 Weir at station 20 and 3 and its stage-discharge rate relation. Runoff 41

Fig. 7.6 Areas of land classification units in thirty-three drainage basins.

3.0 in 4 whereas 80 of that contributes the hours, % area stage-discharge relation is plotted as a relation of

1 to slow runoff with = 90 in 4 hours = 15 runoff a j (or j intensity (mm.day ) to stage height (cm).

days). Since no rain hyetographs were available, daily pre- cipitation, measured in Restanca (1982 m), which sta-

7.6 - J values of the Pontet de Rius basin tion is situated on the border of the Pontet de Rius

had Zeilmaker (1966) analyzed available hydrographs of area, to be used. According to the area-altitude distribution of the Pontet de Rius the small Pontet de Rius catchment area (station 20), area (fig. 7.4), the situated in the Upper Valarties river. This area has Restanca precipitation in the form of rain should be 1.07 in during the observation years 1961—1963 a surface multiplied by percent order to obtain the of 6.1 km2 while correct value The annual its altitude ranges from 1595 m to precipitation (fig. 6.6). is about 2750 m above sea level. Pontet de Rius forms the evaporation, however, 20—30 of the upper percent total Restanca and since part of a glacial valley. The area-altitude distribution precipitation at regional and the hypsometric integral of the area are shown in variations in precipitation intensity are unknown, the fig. 7.4. uncorrected Restanca value has been assumed to be The enclosed land classification shows barren for the Pontet de Rius map 26% representative area. rocks (granite); 39 % scree; 7 % grassland and 28 % An approximate value for the slow runoff reservoir rocks with At with coefficient obtained from 18 sparee trees. a weir, equipped a was depletion curves float activated the of number of successive water stage recorder, discharges during a dry days. The slow the Pontet de Rius area were registered until the flood runoff can be characterized by j = 15 days. The of August 3, 1963. In fig. 7.5 the weir is shown and exact fast runoff reservoir coefficient could only be 42 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 7.7 Runoff analysis of the Pontet de Rius basin.

calculated by means of four precipitation values.

Therefore the Restanca daily rain precipitation values

had to be divided according to theregistrated precipi-

tation hours of Viella. The distance Restanca-Viella

is however 9,5 km and the daily precipitation distribu-

tion of Viella did usually not correspond with the Fig. 7.8 Relation ofbaseflow and percentage ofthe precipi- de runoff from the Pontet de Rius basin, except for the tation, contributing to the fast runoff of the Pontet Rius basin. case shown in fig. 7.7. The runoff characteristics are:

20 % j = 3,0—4 hours and 80 % j = 90,0—4 hours.

Instead of = base 80 % j 90,0—4 hours, a constant

flow of 1.25 mm in 4 hours can be assumed. The

observed runoff does not show a time-lag with respect

to the calculated runoff.

7.7 Relation of runoff, land classification and morphology in

Pontet de Rius

The analysis of twenty-three runoff peaks demonstrat-

ed that the of the contrib- percentages precipitation,

uting to the fast runoff in the Pontet de Rius area are

a function ofbase flow On (fig. 7.8). logarithmic paper broken a line was obtained, indicating that the base flow and the of the fast runoff percentage have no linear After snowmelt in relationship. the June, an important base flow coincides with the maximum

of percentage the precipitation as fast runoff (40 %).

That percentage decreases suddenly in July (15 %) Fig. 7.9 Length profile of the Valarties River upstream and in August-September (10 %). Figure 7.9 shows from station 20. the explanation of this phenomena. The Upper

Valarties valley is a glacial valley with a step-shaped river profile, in which three reservoirs, filled with neck shaped bottoms, damming up the water at the

glacial and torrential material, have been cut out by downstream ends in the summer after the snow melt the glacier. Those reservoirs can reach depths of period. If the Pontet de Rius area is divided according 25—40 be concluded m. They are all characterized by their bottle- to its three glacial steps (table 7.3), it can Runoff 43

Table 7.3. Distribution of land classification units in the Pontet from the Aigüestortes basin and therefore the main de Rius basin problem concerned the precipitation data.

The nearest meteorological station to the Aigüestortes Percentage Scree and basin was Restanca and the problems, discussed in the of total to Subarea Barren rocks disseminated Pontet de Rius analysis, appeared be even more drainage trees complicated, since Restanca was situated in another basin valley.

From the depletion curves 1961—1963 approximate 1 33 15 85 — values calculated. coefficient of j were The storage 1 +2 56 24 76 the fast runoff appeared to b; j = 3,0 —4 hours where- 1+2 3 84 36 64 + the coefficient of runoff has value as storage the slow a 1+2+3+4 100 40 60 of j = 72—4 hours.

Comparison of the results of Aigüestortes and Pontet

de Rius shows that the fast runoff for both basins has

that the — of differences area of the barren and vegetated scree deter- the same j values, independently the mines the of the contribut- in land classification characteristics The percentage precipitation (table 7.4). ing to the base flow, whereas the barren granite rocks total surface of barren rocks however, is for both

produce the fast runoff. basins almost equal.

The slow runoff is faster in Aigüestortes (j = 12 days)

= 7.8 J - values of the Aigüestortes basin than in Pontet de Rius (j 15 days). This is dueto the

three times scree volume of the Pontet de Rius The Aigiiestortes catchment area is situated in the greater

2 basin and to the simpler river profile of Aigüestortes, Upper Aiguamoix glacial valley. The area is 6.1 km

which basin shows no and the altitudes m valley steps. ranges from 1772—2545 above It be concluded that the of the Pontet sea level. can steeper slope de Rius with the basin, The area-altitude distribution and the hypsometric basin, compared Aigüestortes

does not affect the slow runoff, nor the fast runoff. integral of the Aigiiestortes basin are shown in fig.

7.4. The enclosed land classification shows 31 map %

7.9 J - values the Upper Negro basin conifer forest; 30.5 % grassland; 16.5 % barren rocks of 12 9.5 rocks with The of (granite); % scree; % dispersed Upper Negro catchment area has an area and lake. 2 trees 0.5 % 24.4 km . The altitudes range from 1250 m (gauging

Since the weir at Aigiiestortes (station 3) is ofthe same station 12) to 2623 m above sea level. The hypso-

construction as that near Pontet de Rius, fig. 7.5 can metric integrals of the area are shown in fig. 12.2. be used for this runoff analysis. No hyetographs The land classification map (see enclosed map) shows

to the available 56 corresponding hydrographs, were percent grassland and 21 percent scree (table 7.4).

Table 7.4. Distribution of land classification units in ten drainage basins of the Valle de Aran

Percentage of area, contributing to

fast runoff fast base flow slow base flow

River and number Area, km2 of station gauging barren rock barren rocks + disseminated barren rocks disseminated forest + scree scree + trees + trees grassland

Iñola (6) 31.9 14 17 84 12 15

Negro (13) 34.4 5 8 63 19 36 Barrados (16) 59.0 18 19 65 13 34

Garona de Ruda (2) 50.5 21 28 63 17 35

Upper-Valarties 19.4 53 62 65 22 23

(20 +9+10) Upper-Aiguamoix (3) 21.0 55 61 72 11 24

Upper-Negro (12) 24.4 7 11 67 21 31

Lower-Negro (13—12) 10.0 0 0 51 11 40 Aigiiestortes (3) 6.1 17 26 49 12 43

Pontet de Rius (20) 6.1 26 53 53 39 40 44 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 7.10 Average monthly runoff variation coefficients for eight basins. Runoff 45

available from station Since no hydrographs were 12, and a morphological analysis was carried out. The number of of results tables in 2.1 a depletion curves during a sequence are summarized in 7.4 and fig.

dry days in 1962 had to be drawn by means of only and fig. 7.6.

one daily runoff observation. The reservoir coefficient Since 43 % —93 % of the runoffof the eight analyzed

of the fast runoff could not be calculated, but the j- drainage basins in the Valle de Aran consists of slow

runoff amounted = runoff base runoff variation value of the slow to j 16.5 days. or flow, the monthly of the slow runoff of the coefficients information about the annual The j-value Upper Negro give pro-

= than slow runoff in base flow variations. basin (j 16.5 days) is greater the gression

value of the Aigüestortes basin (j = 12 days) and the We have analyzed the relation of maximum variation

Pontet de Rius basin (j = 15 days). coefficients to land classification and morphology in Rius basin has 7.11. It that the maximum base flow Since the Pontet de a larger scree area fig. appears than the the variation is determined the total of (39 percent) Upper Negro (21 percent), by percentage scree contradict former results. and forest Areas covered with runoff analysis seems to area. largely scree and thickness of the how- have small base flow variations. The average scree Upper Negro forest, On the other

has been calculated to be three times that of the hand it be shown that of barren ever, can a greater area

Pontet de Rius basin. Moreover the Upper Negro rocks (with disseminated trees) produces a slight in-

River flows for a distance of three km under its own crease in base flow variation. No relation exists be-

five base flow scree and the river profile shows steps produced tween variations and the average weighted by the former glacier. slope. These results confirm the conclusions of sections

From the analysis of three small high mountainbasins, 7.6—7.9. it be conluced the ofthe can that percentage precipita-

tion, which contributes to the fast runoff is related to

slow the area of barren rocks, whereas the percentage

runoff is related to the relative areas of scree and

forest.

The reservoir coefficient of the fast runoff is approxi-

mately constant and small (j = 0.5 day), while the

reservoir coefficient of the slow runoff (j = 12—16.5

day) is great, variable and largely determined by the

scree volume.

7.10 Monthly runoff variation coefficients of eight representa-

tive drainage basins

defined The monthly runoff variation coefficient is as

the ratio of the to average monthly discharge (mm) the annual divided 12. average discharge (mm), by Fig. 7.11 Relation of maximum runoff variation coeffi- of basins have been Three groups analyzed (fig. 7.10): cients to land classification units.

1. The Iñola- Negro- Barrados- and Garona de Ruda- km 2 7.12 Flood basins, ranging in area from 31.9—50.5 . frequency Valarties- and 2. The Upper Upper Aiguamoix- Up- From four representative runoff gauging stations (3,

in from 19.4— per Negro-basins, ranging area 7 —7a, 8—8a, 13) in the Valle de Aran the frequency 2 24.4 km . of annual floods have been studied according to the

3. The Upper Negro- Lower Negro- and the entire method described by Powell (1943) Dalrymple (1960) from 10.0—34.4 km2 Negro-basins, ranging in area . and Benson (1962). It should be emphasized that the

method provides a measure for the recurrence interval

All rivers show the tremendouseffect of the snow melt for floods of given size. The curves shown in fig. 7.12

runoff or depending on the during May June, average are discharge curves, derived from momentary peak altitudes of the basins. The second runoff maximum rates of flow. Plotting positions for the frequency scale in November December under influence of occurs or were obtained by applying the "California method". the The minimum runoff in precipitation. February (Calif. Dept. Public Works, 1923; Jarvis and others, with the minimum precipitation. corresponds 1936). The logarithmic ordinate scale, as shown on

Each of the basins is for a certain U.S. Geol. eight representative form 9—179b of the Survey, was used and kind of land and in classification, morphology geology straight lines have been drawn through the plotted the Central Pyrenees. points. A bar graph showing graphically the length

of records in the Valle de Aran which were used for

7.11 Relation variation and land of coefficients, morphology the preparation of fig. 7.12, is presented in the same in basins A of the variation of the classification eight drainage figure. set curves, showing

In order to study the relation of variation coefficients mean annual flood (Q.2.33) and of the 10, 25, 50 and floods with is shown and drainage basin characteristics, the enclosed land 100 year drainage area as fig. classification scale 1:50.000 7.13. The test of map at a was prepared homogeneity Langbein (1949) was 46 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 7.12 Flood frequency at four stations in the Valle de Arán. Runoff 47

The influenceof the generation of hydroelectric power

on the destructive power of floods is a serious point of discussion in the Valle de Aran. Before it started,

a certain equilibrium between transported sediment

existed. The mass and discharged water mass energy

distribution within the stream system has changed

a result of the withdrawal. fundamentally as energy

In 1947 for instance, 6 percent less energy was avail-

able for sediment transport whereas in 1964 already

39 percent less energy was available, compared with ofthe theaverage potential energy 1945—1965 annual If precipitation. we assume an average specific degra-

1 dation of 150 mm. 1000 year" (see 2.3) during the of 3 period 1945—1965, a volume 0.4 km has not been transported, that otherwise would have been discharg-

ed out ofthe Valle de Aran. This leads to a progressive

of the filling stream system. 3 _1 of Since the maximum intake (m s ) the hydro- of electrical system does not exceed 30 percent the

mean annual flood (Q2.33) at any intake for a power it is clear that the does station, hydroelectrical system

not work during important floods. No flood reser-

voirs are present in the Valle de Aran. It can be concluded that the sediment load of future floods will

increase due to hydro-power generation, because more Fig. 7.13 Relation of magnitude of floods and drainage sediment remains in the basin. trapped valleys.

The flood of August 3, 1963 for example was only 10

percent greater in magnitude than the flood of June it found that the data 1922 in the Valarties Arties but its effect applied to the records and was 8, near were flood of for are reasonably homogeneous. The flood analysis in extremely disastrous. The August 3, 1963 Garonne in the Valle de Aran shows that floods are frequent but the Arties was only a moderately severe local phenomena. Destructive floods tend to increase flood which normally occur every five years, but its direction. effects disastrous. in relative size in a downstream were very

Table 7.5. Characteristics of fourteen lakes in the Upper Aiguamoix area

Overflow Catch- Max. Min. precipita- Number ment Storage Lake equipped Branch Name of lake tion for storage storage 3 of lake area X 10« m with discharge elev. (m) elev. (m) catchment (km 2 ) area (mm)

Ratera 1 2464.95 2453.0 1.15 0.520 453 tunnel

Pulgar 2 2423.60 2413.0 0.40 0.330 824 tunnel

Aiguamoix Ubago 3 2221.50 2189.0 2.82 4.190 1485 dam + tunnel East Cavidurnats 4 2165.20 2161.0 0.16 0.160 1000 tunnel

Llarg 5 2156.50 2142.5 0.60 1.053 1750 dam + tunnel

Manyera 6 2161.50 2161.5 0.68 0.518 762 dam + tunnel

Clot 7 2132.00 2112.0 0.44 0.648 1474 dam + tunnel

Gelat 8 2562.75 2558.0 0.46 0.130 283 tunnel

Occidental

Superior 9 2390.90 2385.5 1.15 0.098 85 tunnel Aiguamoix Occidental

West Occidental 10 2286.95 2282.0 2.10 0.072 34 tunnel

Tort Central 11 2417.15 2413.5 0.13 0.070 500 tunnel — — Bergils 12 2178.75 2178.8 0.92 natural overflow Caldes 13 2184.55 2180.5 2.23 0.107 479 tunnel

Mayor 14 2098.25 2070.3 1.26 2.806 2010 dam + tunnel 48 H. Rijckborst: Hydrology of the Upper-Garonne basin

7.13 Flood routing through 14 reservoirs in the Upper Aiguamoix

The Upper Aiguamoix catchment area is a severly which has been glaciated granite area utilized by the station of Arties since 1954. In that power area many been the former lakes have worn out by Aiguamoix

glacier and the lakes constitute natural reservoirs for

the hydroelectrical usage (fig. 7.14). By means of five

small arch dams, ranging in altitude from 13 m to

20 m and after the construction of tunnels for a total

of the of lakes length 1.5 km, system in the Upper has been transformed into Aiguamoix a hydrologie

6 3 unit with a regulating capacity of 10.7 10 m .

The unit consists of two Upper Aiguamoix branches, 7.15 Relation of Fig. the inflow and storage in the Upper east and Aiguamoix west, connected by Aiguamoix Aiguamoix area. The lowest 582 m of tunnels. reservoir, Lake Mayor,

is situated in the Aiguamoix west branch. Lake Mayor

discharges into a 1927 m long tunnel, leading to the

Valarties river. The adjacent Upper Garona de Ruda

river on the other hand discharges into the Aiguamoix

east branch through a tunnel with a length of 1270 m.

The characteristics of the lakes in the Upper Aigua-

moix area are listed in table 7.5.

In order to study the hydrological characteristics of

the Upper Aiguamoix unit, the lakes were assumed to

be empty and the discharge tunnel closed. In that maximum case, the water storage in Aiguamoix east

amounts to 6 3 7.419 . 10 m whereas the water , storage

6 3 in Aiguamoix west has a value of 3.283. 10 m .

After a period of inflow (1205 mm for Aiguamoix

east and 435 mm for Aiguamoix west), the lakes are filled and the water storage decreases to zero. This is shown graphically in fig. 7.15.

Assuming a 10 year cloudburst of 150 mm in 2 days (fig. 6.2), the 10 year-safety limit for the Upper

Aiguamoix system can be evaluated with fig. 7.15. In

order to avoid a destructive overflow flood from the

Upper Aiguamoix into the Lower Aiguamoix, it is

to for 150 necessary keep storage space two days, or in the mm Upper Aiguamoix. Moreover it seems

advisable to for keep storage space a constant inflow of 3 _1 2 m .s from the Garona de Ruda, and it is essen-

tial the 3 _1 to keep discharge tunnel (7.5 m .s ) from the

Aiguamoix to the Valarties closed (fig. 7.14). This

implies that the level of lake Ubago under normal

conditions of exploitation should never exceed the elevation of 2214 m (7.50 m under the crest of the

Fig. 7.16 Flood routing through the Aiguamoix west

7.14 Reservoirs ofthe Fig. Upper Aiguamoix area. branch. Runojj 49

of dam). A similar reasoning for the Aiguamoix west cipitation 150 mm has been routed through the

branch shows, that the level of lake Mayor should Aiguamoix-west branch. Barren rocks constitute 87 % of therefore never exceed the elevation of 2082 m (16 m under the the area, scree 7 % and lakes 6 %; the

crest of the dam). runoff characteristic is 93 % j = 12 hours + 7 %

It should be emphasized that the relation storage- j = 24.12 hours. The results are shown in fig. 7.17

precipitation, in the Aiguamoix-west branch, is much and the rise of the level of lake Mayor without inflow

more critical than in Aiguamoix-east (fig. 7.16). This from Aiguamoix-east nor outflow into the Valarties is shown in the The ratio lake surface is dangerous, since lake Mayor is the lowest storage same figure. of inflow into catchment surface has value of 1:110. No base- reservoir the system. Any the Aiguamoix to a

west 130 certain risks. flow has been assumed in this The results of system, exceeding mm, implies figure. the data of the enclosed land classification the flood with the observations of Using map routing correspond

and applying the results of section 7.8 a two day pre- August 3, 1963.

8. EVAPORATION

8.1 Introduction

The evaporation in the Valle de Aran from 1955—

1965 was estimated with a Penman-type formula. the winter months of the During an important part

Valle de Aran is covered with snow. The evaporation

from a snow surface was estimated with a Dalton-

formula. The also estimated with type evaporation was

the formulas of Thornthwaite (1948-1955-1957) and

Turc (1953).

8.2 Evaporation estimationsfrom meteorological data

A Penman-type formula (3) with a reflection of 25 %

could be used for the estimations of the average monthly evaporation at the stations Cledes, Viella,

Arties, Restanca and Bonaigua.

ne

"A H ra ' . r,

E = ! (3) (see list of symbols). A + y

The data from tables 22, 31, 40 and 5.4 and from fig.

8.1, 8.2 were used. The results are shown in table 8.1 Fig. 8.1 Average monthly temperatures during the period and figure 8.3. The water vapour pressures of Viella 1955—1965. resemble the measured values of Arties if multiplied by 0.75 (see also 5.6). Therefore the more reliable values ofViella used for the The unadjusted were evapora- Aran. wind velocity in the Garonne valley is tion estimations The measured values of determined the arithmetic (table 5.4). as mean of the monthly station the meteorological Viella were assumed to be readings at the stations Cledes, Viella and Arties (fig. representative for the entire air mass in the Valle de 8.2).

Table 8.1. Penman monthly evaporation values (mm) during the period 1955— 1965

Station J F M A M J J A S O N D

Cledes 29 43 82 106 126 130 136 152 98 59 40 41

Viella 25 35 80 108 130 140 146 151 96 60 39 40

Arties 24 37 73 93 127 137 142 147 99 55 33 31

Restanca 1 17 41 61 86 108 114 122 75 27 8 13

Bonaigua 4 19 13 53 79 104 104 106 62 28 9 1 50 H. Rijckborst: Hydrology of the Upper-Garonne basin

tions for Restanca (elev. 1982 m) and Bonaigua (elev.

2072 m) are shown in figure 8.3.

Thornthwaite's (1948, 1955, 1957) and Turc's (1953) formulas used for estimations of the were the average annual evaporation during the period 1955—1965. Penman The obtained values were compared with the

and Penman-Dalton values in table 8.2.

8.4 Mountain shadow and orientation of the valleys

calculated the month- Brugman (internal report, 1966) radiation Fig. 8.2 Average monthly wind velocity during the period ly decrease in outer atmosphere shortwave

1955—1965. H on a bottom at Mar in ( oa sn) glacial valley Lago

order to determine the shadowing effect of the sur-

8.3 estimations the snow cover mountains The in the Evaporation from rounding (fig. 8.4). percent error

The evaporation from the snow cover during the monthly evaporation (Penman) is shown in figure 8.4.

1955—1965 estimated with a In the of the error in the total annual years was Dalton-type case Lago Mar, formula (4) for the stations Restanca and Bonaigua evaporation amounted to 16 percent during the water (Dalton, 1802).

wa — wa = of E f (u ) (P ] sa P ) (4) (see list symbols). 2 z z Table 8.2. Comparison ofPenman-, Penman-Dalton-, Thornth-

For the months with an air below average temperature waite- and Turc- annual evaporation values (mm)

0° the air at an elevation of 1.50 m C, temperature during the period 1955— 1965 above the earth surface was assumed to equal the

surface The Penman wind mean snow temperature. Penman- Thornth- Station Penman Turc function f was it has not been Dalton waite (u 2 ) used, although yet adapted to mountainous terrains. Measurements of Williams (1963) and Priestley (1963) seem tojustify Cledes 1042 1042 646 512 the ofthat function. The surface use snow temperature Viella 1050 1050 653 520 assumed be 0° C. the months with was to during a Arties 998 998 607 467 mean air temperature above 0° C, according to Restanca 673 456 337 366

Martinec, Wartena, Brugman & Zeilmaker, (1966). Bonaigua 582 402 288 302 The combined Penman-Dalton evaporation estima-

values. Fig. 8.3 Average monthly Penman-evaporation values and combined Penman-Dalton evaporation Evaporation 51

8.5 Short wave radiation measurements

During the summer of 1965 daily shortwave radiation

measurements were carried out at Restanca (H sjj) (elev. 1982 m) and Viella (elev. 931 m) with Gun

Bellani solarimeters. The results generally indicate

higher values than those from the tables of Penman

(1960) and Slatyer & Mc Ilroy (1961) which we used

for the calculation of the evaporation as listed in table values 8.1. The measured H h are s compared with the calculated H values in 8.7. sh figure

Recent net radiation measurements (Hj by Schröder

& van Rooyen (internal report, 1967) carried out

with a Kipp solarimeter in the High Pyrenees near Andorra confirm the results obtained in the Valle de

Aran. According to Martinec, Wartena, Brugman &

Zeilmaker (1966) this is probably due to the high

of the in this The transparancy atmosphere area. Penman evaporation values, estimated from the

measured H values of table 8.3 are 23 higher sn percent

for Restanca and as much as 52 % higher for Viella,

if compared with the evaporation values of table 8.1.

8.4 decrease in outer shortwave measurements Fig. Monthly atmosphere Table 8.3. Short wave radiation in Restanca and

radiation bottom and in the (oaHsh) on a valley error Viella during 1965 with Gun Bellani pyranometers

Penman values due mountain 1 monthly evaporation to (in cal. cm-2.day- ) shadow (1965).

Rcstanca balance 1964—1965. This is for 10-day Viella year error typical period cal.cm^.day- 1 cal cm-'.day-' nearly all glacial valley bottoms in the Valle de Aran because of the Mar has the average slope Lago area only a moderate value of 26°. 11-6/20-6 535 The effect of the orientation of the valleys on shadow 21-6/30-6 550 636 studied and the results shown in patterns was are 1-7/10-7 516 625

8.5. It shows the of shadowed areas figure percentage 11-7/20-7 422 558

in the Valle de Aran the winter solstice at 12 during 21-7/31-7 476 600 hour (17 %). The relation of the percentage shadowed 1-8/10-8 470 628

of 31 basins to be 360 527 area and the average slope seems 11-8/20-8 independent of the orientation of those basins (fig. 476

8.6).

1955 — 1965 Table 8.4. Average monthly percentage of the Valle de Aran, covered with snow during the period

J F M A M J J A S O N D

% 75 75 45 45 13 3 0.5 0.5 3 13 45 75

Table 8.5. Dalton monthly evaporation values (mm) from a snow cover at Restanca and Bonaigua

Station J F M A M J J A S O N D

— — — 0 0 18 Restanca 0 3 7 3 6

Bonaigua 0 3 0 12 0 — 0 0 11 52 H. Rijckborst: Hydrology of the Upper-Garonne basin

8.5 Shadowed Valle winter solstice 12.00 h. Fig. areas in the de Arán during the at

8.6 of shadowed Fig. Relation the percentage area during the winter solstice and the of 31 average weighted slope

basins.

Fig. 8.7 Comparison of calculated and measured short-

wave radiation (Hsh). Evaporation 53

8.6 Actual evaporation estimations Table 8.6. α-values, estimated for the Valle de Arán

In figure 8.8 the average elevation of the monthly C-isotherm the is shown. 0° during years 1955—1965 land M,J,J,A N, D, J, F classification O The percentage of the Valle de Aran, covered with M, A, S, summer winter listed table units snow, is in 8.4. The Dalton monthly evaporation values of table 8.5 In can be applied to the areas above the 0°-isotherm. Barren rocks 1.0—1.1 1.0—1.1 1.0—1.1 the which lie bïlow the the areas, 0°-isotherm, monthly Scree 1.0—1.1 1.0—1.1 1.0—1.1 Penman values of table 8.1 can be evaporation (E 0) Barren rocks used. On the land classification the area of map, and scattered

the units below a certain 0°-isotherm be can small groups determined. The actual was esti- evaporation (E ac) of trees 1.0—1.1 1.0—1.1 1.0—1.1 of the E values the a-values Arable land 1.1 — — mated, by multiplying 0 by

table 8.6. Deciduous

It should be that the Penman trees and emphasized, evapora- brushwood 1.2 0.7 1.1 tion values can only be applied to wet surfaces. Hence Conifers 1.1—1.2 1.7 1.5 during the summer period, the actual evaporation in Grass and the Valle de Aran is always less than indicated. The scattered small relation of the evaporation frombarren rocks to runoff of trees 1.1 0.9 1.0 groups measurements is reported by Martinec, Wartena, Grassland 1.0 0.8 0.9 Brugman and Zeilmaker (1966).

The annual E for the is estimated to average ac valley

be 500—550 mm during the period 1955—1965.

Fig. 8.8 Average height of the monthly 0°C-isotherm during the period 1955—1965. 54 H. Rijckborst: Hydrology of the Upper-Garonne basin

9. GLACIERS OF THE ANETO GROUP

9.1 of the ofthe Aneto the of 1958. Fig. Position glaciers group during summer

9.1 Introduction 9.2 Precipitation on the glaciers

The of this is to estimate the The annual the purpose chapter precipi- average precipitation on glaciers,

tation and from the and to evalu- which have elevation of 3000 evaporation glaciers a mean m, amounts to

ate the 2500 the snowmelting processes although only sparee m during period 1946—1966 (fig. 9.2). If available. data are we apply the precipitation coefficients of the nearest The six ofthe Aneto situated the glaciers group are at meteorological station, Restanca (elev. 1982 m), to base of the mountain in the the Aneto it highest peaks Pyrenees. area, is possible to estimate the average location indicated Their have Their is in fig. 8.8. names monthly precipitation. been derived from the six which rise An of steep glacial horns, important part (43 percent) the measured above the ice The Aneto is the is masses. group composed precipitation on glaciers snow. However, of the the Alba-, Maladeta-, Aneto-, Tempestats-, according to figure 6.7, the assumed snow drifting The Russell Salenques- ,and Russell-glaciers (fig. 9.1). (see also section 6.10) decreases the effective snow flows into the River and is there- rain ratio from 43 32 glacier Ribagorzana versus to percent (Higashi, 1957). fore considered. It is that the When the not remarkable, melting average monthly snowfall coefficients of of the flows karst into Restanca of water glaciers through systems are applied to the glaciers the Aneto

the Garonne River on its way to the Atlantic Ocean, group, the monthly distribution ofsnowfall at the 3000 rather into River into than the Esera which discharges meter level can be estimated (table 9.1). the Mediterranean Sea.

Trails which lead across the glaciers, provide access

to the highest Pyrenean peak, the Aneto (elev. 3404

m). Some people have lost their lifes in efforts to

ascend the mountain.One of them, the French moun- tain died in the of the guide Barrau, upper part

glacier, and his remains were recovered near the base after 107 This estimation of the years. permitted an average annual velocity of about 12—14 meters for the Aneto glacier. It is also possible to estimate the of the from retreat movement glaciers publications by Fig. 9.2 Average monthly rainfall and snowfall in the mountaineers. Aneto area.

Table the the Aneto the 1955— 1965 9.1. Average monthly snowfall (cm) on glaciers of group during period

J F M A M J J A S O N D

112 122 114 120 17 9 — — 1 42 100 165 Glaciers the Aneto of group 55

Table Estimated vertical and elevation 3000 9.2. monthly temperature gradients (°C/100 m) average monthly temperatures (°C) at an of m

J F M A M J J A S O N D

Average monthly gradient in

(°C/100 m) 0.56 0.71 0.89 1.00 1.45 1.45 1.22 1.11 1.45 1.89 1.00 0.64

— 9.1 — 11.1 — 9.9 — — 9.6 — 6.3 — 1.1 — 0.1 — 5.1 — 14.4 — 10.5 — 9.9 temperatures, (°C) 10.2

As result of lower the elevation of a temperatures at

3000 meters, the monthly snowfall coefficients of the

glaciers are not equal to the coefficients of Restanca.

The areal variation of the rain-snow ratio (in percent)

in the Aneto area and in the Upper Esera valley is

shown in fig. 6.9. A significant increase ofsnow precipi- is tation in a downslope direction from the glaciers indicated.

9.3 Monthly increase of the 0° C-isotherms

1955—1965 the increase of the From average monthly

0° C isothermhas been estimated from the temperature readings ofthe meteorological station Restanca, which

is situated 17 km east of the Aneto glaciers. Table

9.2 shows the applied vertical temperature gradients, as well as the estimated average monthly temperature at an elevation of 3000 meters. In general, the vertical from temperature gradients Restanca to Bonaigua have been for (1955 —1965) used, except February and December. The position of the 0° C-isotherms in the summer is shown in figure 9.3. The 0° C-isotherm for the warmest month does not reach the 3000 meter level. The maximum elevation of the warmest month is 2790 meters. Therefore this isotherm outlines roughly the region of snow accumulation. An im- pression of the snow cover in June between the eleva- tions 2200 m—3000 m can be obtained from fig. 9.4, which shows the high mountains of Lago Mar.

Fig. 9.4 Snow cover in the Lago Mar area (elev. 2200— 3000 m) in June 1965.

and 9.4 Snow depth snow density

The Martinec equation has been used to estimate the

snow depth and snow density on the glaciers.

3 h = h .t-°- t 0 (Martinec, 1965).

h = snow depth after the elapse of t days. t

h = 0 original snow depth.

The results are shown in figure 9.5. They indicate an

average annual snow accumulation of 1.60 m. Since

no actual snow depth data are available from the

Aneto glaciers, it is not possible to check the results. Faura measured the annual (1932) snow depth during

the winter 1923—1924 and found a value of 1.50 m Fig. 9.3 Position of the 0°C-isotherm in the Aneto area

the elevation of 3000 meters. during the summer months. near 56 H. Rijckborst: Hydrology of the Upper-Garonne basin

Estimation ofthe the Aneto Fig. 9.5 average annual snow accumulation on glacier.

The snow melting processes cannot be evaluated due area, because the difference in elevation is too high. lack of data. the the months continuous flow of to accurate temperature However, During summer a

ofthe indicatesthat the water from the air to the surface present position glacier melting vapour snow was of above assumed and correction factor of 0.5 snow the 3000 m elevation is not very signifi- a was applied

cant, perhaps about 10—20 cm. to the vapour pressures of Viella.

The average ice depth of the glaciers of the Aneto Martinec, Wartena, Brugman & Zeilmaker (1966) has been from aerial measured correction factor of 0.68 Viella group estimated, photographs, applied a to

to be 65 meters in 1948, which corresponds to an data in order to obtain the vapour pressures for Lago of Mar The results of the accumulation the precipitation for 35—40 years, (elev. 2234 m). evaporation- with of The and sublimation-estimations for the Aneto are a snow density fifty percent (fig. 9.5). area average snow density of glacier ice however, is eighty listed in table 9.3. It can be concluded that the subli- of mation is much than the percent, which corresponds to an accumulation the more important evaporation of 80 This value from the in the Aneto precipitation years. corresponds very glaciers area. well with the observed value of 107 years (see 9.1).

9.6 Long term variations of the glaciers

9.5 Evaporation from the glaciers & Faura Sans Forel Eydoux Maury (1907), y (1932),

The elevation of Garcia Sainz Hess average monthly evaporation, at an (1900), (1930, 1935), (1904), Hey- 3000 has been estimated with brock Liado Michelier meters, a Dalton-type (1933), Llopis (1946), (1885),

the Nussbaum Penck Solé Sabaris formula, applying average monthly temperatures (1933, 1956), (1883), of table 9.2 and the Penman wind function f Soler Santaio (1933), Trutat (1877) and (u 2) (1957), y values from Restanca, (chapter 8.3). In the Dalton Vallot (1887) give information about the glaciers of formula the uncorrected from the Aneto and the term variations in size water vapour pressures group long Viella (elev. 932 m) was not used for the Aneto of the glaciers in the Pyrenees.

9.3. and the Aneto Table Average monthly evaporation- sublimation values (mm) for area

J F M A M J J A S O N D Year

evaporation

(mm) 17 10 4 0 0 0 0 5 0 0 0 20 56 sublimation

(mm) 0 0 0 5 23 22 13 0 14 32 9 0 118 Glaciers of the Aneto group 57

From all those it that data can be concluded, the

of the Aneto reached maxi- glaciers group probably a

mal areal extent between 1780 to 1790. We could not

obtain information earlier than 1780. The glaciers — retreated from 1790—1850, advanced from 1850

1860, but retreated until 1890. An advance was ob-

served in 1890, but since that year the glaciers are from retreating. The Maladeta glacier retreated an

elevation of 2286 m (in 1809) to 2550 m (in 1870),

indicating an average annual retreat of four meters. Data of the FECSA 30 confirm those over years

measurements.

In figure 9.6 the areal extent of the Aneto glaciers in various is shown. The small Russell which years glacier

flows into the Ribagorzana River and the small trans- which fluencing Aneto-South or Coronas glacier, flows

into the VallibiernaRiver, are not shown. The position

of the glaciers around 1810 has been deduced from old whereas an picture (Solé Sabaris, 1962), the posi-

tion in the years 1928, 1948 and 1958 has been derived from topographical maps (scale 1:50.000). The situa-

tion in 1948, which is partly indicated on the enclosed

land classification map, indicates an advance, whereas in evident. 1958 an important retreat is Long term

precipitation measurements in the Valle de Aran are

available from a Mougin rain gauge in Lés (elev. 630 The data from 43 shown in m). years are figure

9.6, which indicates no significant decrease in precipita-

tion during the period 1922—1966.

9.6 Areal Fig. extent of the Aneto glaciers in various Fig. 9.7 Long term precipitation measurements (1922— periods (1810, 1928, 1948 and 1958). 1965) from Lés.

10. THE AIGUAMOIX DAM

10.1 Introduction The system is indicated on the enclosed land classifica-

The dam and reservoir have been tion The water from the lower Iñola, Aiguamoix designed map. system uses for the regulation of the water flow to the Arties power Garona de Ruda, Aiguamoix and ValartiesRivers. The station. The rock-fill is maximum waterflow of the Aiguamoix dam 30 meters high permitted system amounts and to 3 _1 at the Aiguamoix reservoir has a capacity of 500.000 12 m .s and its hydraulic head Arties reaches 3 The reservoir m . can control a maximumwater depth a value of 247 m. However, no permission has been fluctuation of 12 meters. The construction of the dam given yet to fill the Aiguamoix reservoir, which is began in 1963 and it was completed in 1966. The probably due to the Vajont disaster in October 1963. dam and its reservoir form of The contribute better under- Aiguamoix now part following study may to a the "Salto del Aiguamoix" system, which comprises standing of the construction of the Aiguamoix dam

14.000 meters of tunnels and four small rockfill dams. (fig. 10.1). 58 H. Rijckborst: Hydrology of the Upper-Garonne basin

10.1 of the dam. Fig. Topographical map Aiguamoix

The axis of the 10.2 Topography and geology shaped granodiorite mass (fig. 10.1).

bottle neck is situated 40 meters west of the present The entire footing of the Aiguamoix dam consists of Aiguamoix River, whereas its highest point is exposed granodiorite rubble and it was shaped by torrential 40 meters north of the dam. and glacial erosion. The reservoir, south from the The bed rock at the dam site has been investigated by dam site, is situated in the so-called "llano" Aigua- 700 meters of diamond-drilling and three shafts. moix. The "llano" forms a part of the flat glacial bottom valley and it has the characteristics of a lacus- 10.3 Development of the project trine depression in glacial material, which developed The reconnaissance that the overbur- after the final withdrawal of the Pleistocene Aiguamoix survey showed, den make excavation feasible. A The contained was too thick, to glacier. depression a lake, which had a

rock fill dam rather than one founded on bedrock was high water elevation of 1415 meters. It was 400 m therefore selected. wide, 860 m long, and 25 m deep and it was rapidly filled material. The could Since abundant granodiorite scree masses of high up by glacial lake sediments

available a distance of 800 be observed during the dam excavations. The down- quality were at only meters, to it was decided to fill the dam with scree and seal stream end of the lake was situated 50 meters north the face with from the dam. a nylon-concrete cover. present Aiguamoix upstream Later deformations of the lake sediment have been Three drainage tunnels were designed, involving a

total of 370 meters. The left bank-, the dam- observed in the right bank of the Aiguamoix River, length and the right-bank-tunnel have also been used for 140 meters south from the dam, which indicates a The tunnels into the bottom drain- later advance of the glacier. The lacustrine- and grouting. discharge of the dam. glacial-material is, over a depth of40 meters, dissected age Aiguamoix by the Aiguamoix River (Fig. 10.2 and 10.3). the The foundations of the Aiguamoix dam could be 10.4 Watertight screen and drainage of foundations studied the excavations. shows 2 consists during Figure 10.4 The principal watertight screen (12.800 m )

profiles of the left bank. The alluvial materials on of a total of 2140 meters of grouted diamond drill which the dam has drill holes been built, rest on a bottle-neck- holes. The initial spacing of the diamond Fig. 10.2 Fluvio-glacial material in the left Aiguamoix bank at the dam axis (elev. 1400 m)

Fig. 10.3 Fluvio-glacial material in the left Aiguamoix bank, 700 m south from the dam. 60 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 10.4 Geological profile of the left Aiguamoix bank at the damsite.

the and in the was 6 meters, whereas the secondary holes were placed inch drilled filter drains under dam intermediate left and bank. drilled from the drain- at positions. right They were tunnels and with filters. No The maximum injection pressures were fixed at 10 age equipped special ~ 2 drains have been drilled the downstream face of kg.cm between 0 and 10 m depth, increasing by on 5 2 5 of Pressures the dam. kg.cm per meters depth. were

2 limited to 20 kg.cm below 25 meters in depth in order avoid risks ofunwanted 10.5 Water permeability tests to any possible breaking into the The carried out ground. injection was normally Water permeability tests at the Aiguamoix dam have

out in five meter sections, starting from the bottom been carried out in 22 reconnaissance drillings by of the hole. The entire involved the with obturator.The watertight screen means ofa pumping-in method one of 93 3 which injection m cement, means an average method comprised a closing of the upper end of a drill

metre of 95 The into the absorption per kg. average cement hole with that obturator. Water was pumped

2 2 absorption m screen amounted to 16 Maxi- hole under of 5 and water losses in per kg. a pressure kg.cm' cement losses the mum during grouting procedure 10 minutes over the entire open sounding under the -1 amounted 2760 The of water- to kg.m . height the obturatorwere measured. Those losses were calculated

varies between 5 and _1 _1 tight screen 45 meters, averaging in liter.min meter The obturatorwas then dropped .

16 meters. 3.50 m and the same procedure repeated until the A uniform grouting procedure was used during the bottom of the drill hole was reached. Heitfeld (1965)

dam construction. The cement was tested quality describes the errors inherent in this method. At the

A that the continuously. rough test demonstrated, Aiguamoix dam some of the errors have been reduced increase in cohesion of the considerable The screen was by decreasing the interval by 50 percent. pump- after the grouting. had be rectified the Heitfeld ing pressures to using Since — no precise information about the heterogeneous (1965) graphs. After correcting the water loss and the of the different of the founda- glacial deposits arrangements measurements, it was found that 45 % in the banks could be the strata supporting obtained, tions have water losses below 3 Lugeons (= 3 liter.

1 1 2 grouting program met with a success largely because min- .meter- at 10 kg.cm- ), which is acceptable. of the skill and of the great experience The to be operators. remaining 55 %, however, appeared very The quality of the granitic rock under the fluvial permeable and occasionally water losses of 250 liter.

1 -1 -2 meter at were measured. glacial deposits is excellent. The granite is an almost min . 5 kg.cm By apply- unaltered NW-SE Heitfeld the loss compact rock with a and NE-SW ing the analysis of (1965) to water The of chemical ofthe foundations could joint system. zone slight weathering values, a permeability pattern the of the reached of the of the reconnais- on top granite a maximum depth be obtained. The results study of 10 The of and meters. average percentage core recovery sance drillings, water permeability tests cement remained at about 80 percent. The first 5 m of the losses are shown in fig. 10.5, which represents a hydro- dam axis. granite was considerably jointed and permeable. The geological section along the Aiguamoix It of varied shows since the absorptions cement per meter drilling length an approximate permeability pattern, from 0—25 of data the kg. errors in the interpretation the concerning The drainage of the dam foundations involved 4.5 extreme heterogeneous glacial material do not allow The Aiguamoix dam 61

Fig. 10.5 Hydrogeological section along the Aiguamoix dam axis.

has b:en = vertical distance of the of of the a more precise interpretation. Figure 10.5 Z; centre gravity

used to compute the groundwater flow through the horizontal layer to the impermeable bedrock,

section along the dam axis. (m).

L; = length of the horizontal layer (m). See list of

10.6 Groundwater flow through the ungrouted Aiguamoix symbols dam foundations For the computation of the groundwater flow through

the banks the same was This subject is more a purely academic question rather supporting equation applied with than a practical one, although it probably might have of B + B an application to an analysis grouting procedures. ( ii i2 l

- Ouwerkerk & Aj = D¡. (Van Pette, The construction of the Aiguamoix dam has funda-

mentally changed the groundwater flow in the Aigua- 1966). (6) moix valley. Under normal circumstances, ground- = horizontal distance from the reservoir Bjj average water flow in the glacial valleys of the Valle de Aran to bedrock, (m) is because of the very restricted, hummocky-shaped = horizontal distance from the down- B¡ 2 average profiles of these valleys. stream exposure of the horizontal layer to For the calculation of the laminar groundwater flow bedrock, (m) from the Aiguamoix reservoir through the ungrouted

= thickness of the horizontal dam foundations 10.5 and for- Dj average layer, (m) figure a Darcy type

mula has been used: (5) Water losses from the maximum filled Aiguamoix reservoir under the ungrouted dam would have

3 _1 amounted to 13.000 m .day whereas the losses 0 , - ! = 2 Q AiK;* 3 t (5) m through the left bank would have been 57.000 . i= 1 M -1 and the bank 24.000 1 day through right m^day- .

2 1 After the water losses seem to be re- Qt = daily groundwater flow, (m .day~ ). grouting, largely

duced. This corroborates the of the construc- 2 opinion A; = cross section of horizontal layer (m ). tion engineers, that the heterogeneous glacial material -1 K¡ = ). permeability coefficient, (m. day in the Aiguamoix dam foundations could be made

cement

11. KARST SYSTEMS

11.1 Introduction uce profound changes in the various catchment

In the Cambro-Ordovician and Devonian limestones, areas. For a hydrological study it was therefore a delimit the karst which occupy twelve percent of the Valle de Aran, requirement to systems as exactly as extensive karst have From the and of systems developed (fig. 11.2). possible. geological map profiles

They were described by numerous authors throughout Kleinsmiede (1960) the connections of sinkholes the nineteenth century. The karst phenomena prod- (forats) and springs were interpreted and checked by 62 H. Rijckborst: Hydrology of the Upper-Garonne basin

means of a color tracer. The hydrological charac- sinkholes (forats) are indicated. The forât de la

teristics of the important Giiells del Jueu karst system Renclusa,- Aigualluts,- Toro de Barrancs,- Puerto de

were studied by applying the method of De Jager Benasque are situated in the Upper Esera Valley.

(1965). The forat del Toro de Aran and forat Mall Artiga

are situated in the Jueu valley, whereas the forat Lago

11.2 Geology Negro is situated in the Negro valley.

the Puerto de which dis- The structural geology of the five karst systems has Except Benasque sinkholes, into the Pumero all others drain into been described by Kleinsmiede (1960). Some of the charge springs, detailed the Güells del The Devonian lime- karst systems were mapped on a more great Jueu spring.

scale stone cuts three surficial water divides, including the by Mey (internal report, 1963) and Leniger main one of the between France and Spain (1965). The five investigated karst systems, which Pyrenees the affect (fig. 11.2). In table 11.1 some data about were expected to the catchment areas, Güells del comprise the Giiells del Jueu-, Estua-, Ruda-, Bó-, Jueu system are compiled. Leniger

and Pila-systems. Each system is characterized by the

of its karst In the Valle sink- color tracer the Karst name spring. de Aran, Table 11.2. Results of experiments in

holes are determined by faults, joints and contact systems

planes of limestonesand slates or sandstones. The sink-

holes have been well in the especially developed glacial Water velocity Travel time of depressions between 1900 m and 2300 m. because Name of of fast runoff color tracer and karst and much cold water was available there during the spring (m/hour) year (hour) Pleistocene. of measurement

11.3 The Guells del Jueu system Renclusa— Güells 13 385 (1947) Figure 11.1 shows the complicated structures of the Renclusa— Güells 5.2 960 (1948) Devonian limestones in which the Güells del Jueu Renclusa— Güells 17.2 280 (1948) The ("Jupiter's eye") system developed. important Aigualluts—Güells 12 300 (1947)

Toro de Aran—

Güells 14 150 (1965)

Mall Artiga—

Güells 14 140 (1965)

Toro de Bárranos—

Güells 9 360 (1965)

Lago Negro— Güells 72 57 (1964)

Bargadera—Estua 288 14 (1965) Liât— Pila 327 8 (1965)

150 57 Liât—Pila (1950)

Liât—Pila 285 11 (1948)

Liât—Pila 300 11 (1949)

Liât —Pila 360 12 (1949)

Liât —Pila 260 10 (1949)

Liât —Terme 480 12.5 (1965)

Arcos—Bó 2.5 240 (1965) Fig. 11.1 Structures of the Devonian limestones related to

the Güells del Jueu system.

Table 11.1. Sinkholes in the karst systems

difference in horizontal elevation (m) elevation of Sinkhole (forât) distance to karst slope in degrees karst spring of sinkhole sinkhole and spring (m) karst spring (m)

Rene lusa 2,225 5,000 745 9° Giiells del Jueu Aigualluts 2,100 3,950 620 10° Güells del Jueu

Toro de Aran 2,060 2,125 580 15° Giiells del Jueu Malí Artiga 2,060 2,000 600 17° Giiells del Jueu

Toro de Barrancs 2,300 3,250 820 14° Giiells del Jueu Lago Negro 1,980 4,125 500 9° Giiells del Jueu Bargadera 2,020 3,350 470 8° Estua Liât 2,120 2,650—5,970 340—400 7°—4° Pila-Terme

Arcos 1,960 1,200 160 8° Bo Pudo 2,250 6,750 830 8° Algiiaire-Ruda Karst systems 63

1965) carried out tracer experiments in order to 11.4 The Estua system

determine the connections of the Toro de Aran-, The Estua system occurs in a rather simple Devonian

Toro de Barrancs- and Mall Artiga sinkholes with the limestone structure and it cuts the surficial drainage of Valarties-Rivers. Güells del Jueu spring. The results are listed in table divide the Bargadera- and

11.2. The Devonian structure is described by Kleinsmiede

Belloc Casteret 1931 Lizaur Roldan 1951 the forât de ( 1896), ( ), y ( ) (1960). Only one major sinkhole, Barga- earlier and the F.E.C.S.A. company carried out tracer dera was investigated. The forat is situated near the

experiment in the Renclusa-, Aigualluts- and Lago shore of a lake and the waters flow into the Estua in Negro sinkholes. Their results are shown table 11.2. spring. Results are listed in table 11.2. The Güells del studied Belloc Jueu system was by The (1896), Escher (1953), Jeanbernat and others (1873), 11.5 Ruda system

Lambron & Lezat (1859), Nerée-Boubée (1842), In the valley of the Garona de Ruda River the Ruda-

Reclus (1875) and Trutat (1877). karst system developed in the complicated structures

11.2 of karstified catchment of karst and surficial divides in Fig. Outcrops limestones, areas systems water the Valle de Arán. 64 H. Rijckborst: Hydrology of the Upper-Garonne basin

of the Cambro-Ordovician. The which is The results shown in table 11.2. The structure, accuracy. are

described by Kleinsmiede (1960) as a Cambro- Bó system produces no change in the catchment

Ordovician anticline, does only partly explain the areas.

results of our tracer experiments. Apparently there

karst in the limestones which 11.7 The Pila exists no system connects system

the Rio Malo with the Ruda as could be springs, A complicated structure in the Cambro-Ordovician from Kleinsmiede's profiles. Therefore the expected limestones in the Upper Toran-, Upper Iñola- and Rio Malo system is considered as an independent Upper Barrados-Rivers has been mapped by Klein- The unit, the Bó system. Ruda system is situated in a smiede (1960) and Mey (internal report, 1963). Mey karstified limestone which is intersected severely mass of his (1963) mapped the area in much detail. Two by numerous faults. It is drained by the four Ruda profiles are shown in fig. 11.3. The Liât sinkhole and and the Algüaire (fig. The Cambro springs spring 11.2). the Pila- and Terme-springs are shown in fig. 11.2. Ordovician limestones cut the surficial drainage divide The Pila karst is system developed in the Cambro- of the Garona de Ruda- and the Pallaresa-Rivers. The Ordovician limestones. A tracer experiment showed Pudo sinkhole drains probably water into the Lago that water, entering the forât de Liât sinkhole, flows

Ruda- and In the summer of Algüaire springs. 1965, to the Pila- and Terme-springs. The Pila karst spring

no water entered the Pudo sinkhole and there- Lago (fig. 11.4) is most important and it discharges at least fore could bs carried out. The no tracer experiments three times much the Terme as as spring. It has not water of Lago Pudo discharges into the Garonne been proved that a connection exists between the Pia

rather than into the Mediterranean Sea as River, de l'Ana sinkholes and the Pila spring, but it is quite otherwise would b; expected. reasonable this be Results to expect to true (fig. 11.2).

of recent and former experiments are listed in table The 11.2. 11.6 Bó system

The Rio Malo River is crossed by Cambro-Ordovician 11.8 Tracer limestone in which the Bó system has developed. It experiments

was expected, that the Bó system drained into the Baeyer (1871-a), Bogomolov & Silin Bektchourine

Algüaire spring and thus was part of the Ruda system, ( 1959), Castany ( 1963), Casteret ( 1931), Foster ( 1951),

but this has bsen proven not to be true. Tracer experi- Kaufman & Orlob (1956), Käss (1964), Keller (1961), carried three times in order Lizaur ments were out to assure Knop (1875—1878), Lehmann (1934), y

11.3 of Pila-karst Fig. Two geological profiles the system. Karsl systems 65

Fig. 11.4 Discharge measurement of the Pila-karst spring.

Roldan (1957), Maurin & Zötl (1959), Schlichter of ten dry days. The total cave volume was estimated

and Thomas described be 36.000 3 the water with (1902—1905) Wilson & (1964) to m by multiplying storage tracers for karst and fluoresceine factor 40. This factor the ratio of the a system, appears to a was average section of the and the section of the be the best. Therefore, this tracer was used during the cross caves cross experiments in 1965. The concentrationof the fluor- karst river. esceine was measured by comparing a sample in a test tube with standard solutions in closed test tubes. 11.9 Chemical analyses

An field was inexpensive apparatus designed by J. Karst water chemical tests were carried out with the

with four V two wol- Hogendoorn 1,5 penlight cells, Houseman Palin test kit No. 6. Since the waters in the frame lense lamps, two Kodak light source filters 47 B be Valle de Aran appeared to chemically very pure, and Kodak 58 observation filters. The two parts were the results of the tests could not be interpreted. The fixed in black varnished wooden block and the unit a specific conductance values, measured in August 1965 was fastened in a small box. It to showed reliable appeared possible a more pattern. The conductance reach fluoresceine. The an accuracy of 0.5 ppm. pre- values of the karst waters ranged from 30—160 micro- of standard solutions much attention had paration requires mhos (25° C). Waters, entering the karst systems,

(see also The of the tracer con- Käss, 1964). purpose in general lower conductance values than those dis- centration determinethe measurements was to average charged by the karst springs. As could be expected water ofthe runoffin the karst A variance of the chemical of velocity peak system. however, a great quality Gaussian distribution of the assumed and velocity was the the karst observed. waters, entering systems, was active the distance sinkhole to spring was multiplied by V 2. This indicates an mixing corrosion (Bögli, limestone the karst The average discharge, multiplied by the average 1964) or solution, throughout is of the in velocity a measure water storage capacity systems. of the Devonian and Cambro- the system. Thus for instance in the Bó system, the Representative samples reached value of 900 3 after Ordovician limestones water storage a m a period were chemically analyzed 66 H. Rijckborst: Hydrology of the Upper-Garonne basin

The the Cambro- is situated of the (table 11.3). results indicate that 25) in such a way that the outflows Ordovician limestone is whereas the De- small Pumero- and brooks also very pure, Artiga de Lin are limestone contains insoluble material. of the vonian more registered. In order to obtain the real outflow Thin sections of both limestones show considerable Güells del karst sub- Jueu system, it was necessary to

texture. tract porosity in the sparitic recrystallisation the runoffvalues of those brooks. It was difficult

to study the hydraulic characteristics of the weir and intake tunnel in has been Table 11.3. Chemical analyses of the Cambro-Ordovician- and the Upper Jueu. The weir

Devonian-limestones (weight-percentage). built so that the inflow into the tunnel can never exceed

maximum 3 _1 The maxi- the tunnel capacity of5.0 m s . Karstified mum outflow of the Güells del Jueu spring, is esti- Fe 0 MnO CaO H 0+C0 a 3 MgO 2 2 limestone 3 _1 mated to be 15 m s . Therefore a reservoir analysis of

karst could be carried for low system only out out-

3 _1 Cambro— flows, not exceeding 5 m s . From fourteen recorded in Ordovician 0.3 55 44.4 selected depletion curves

Devonian 2.0 0.3 8.2 42.6 43.8 the period August-December 1962—1965, a relation of j-values of the fast runoff and the baseflow of the

karst obtained The of system was (fig. 11.6). j-values the baseflow in- 11.10 Runoff analysis the fast runoff decrease if related

creases because the is filled with water. During The outflow of the Giiells del Jueu spring is continu- system

the winter, the snow cover can produce a j-value, ally measured in the tunnel to the Benos power station. of karst In A weir and tunnel constitute the intake for this resulting in a greater j-value the system. power order evaluate the the inflow station The recorder to peak storage volume, (fig. 11.5). water stage (station from into the karst system has been calculated the

outflow of the karst spring. Three runoff peaks

were analyzed (fig. 11.7) using j-values, which were

derived from the recorded depletion curves. A con-

Fig. 11.5 Map, showing the situation of the Güells del Fig. 11.6 Relation of the fast runoff and baseflow of the

Jueu karst spring. Güells del Jueu karst system.

Fig. 11.7 Runoff analysis of three hydrographs of the Güells del Jueu karst system. Karts systems 67

inflow twelve hour assumed. Moreover the of stant during periods was percent. evaporation retention water The inflow into the Giiells del is limestonesafter rainfall low in the Jueu system largely on was very summer in basin. Since measured for the the result of rainfall the Upper Esera months of 1965 as Estua system. The

39 percent of the Upper Esera basin consists ofbarren evaporation had values of only 0.5—1.0 mm after table of rocks, (see enclosed land classification map and rainfall, whereas the evaporation retention water

7.2) an important fast runoff can be expected as of the adjacent Pontet de Rius granite area reached inflow into the karst This with the value of 3.0 mm after rainfall. The total system. agrees a average computed inflow curves offig. 11.7. It was not possible annual infiltration on limestones could be estimated

obtain a runoff characteristicofthe from the Pila A of to complete Upper measurements on system. value

and runoff data. -1 Esera due to lack of rainfall 3.0 mm day was computed during 1955 and 1956. The sinkholes of the Giiells del The infiltration is the snowmelt (forats) Jueu system greatest during period been overflow inflow 1 have observed to with a constant (6.3 mm day ) and minimal during the winter (1.9

3 1 1 of 20 m .s after a rainy period. This corresponds to mm.day ).

40 a daily precipitation of 125 mm, if percent of the As stated previously, the baseflow of karst systems in fast runoff. Aran is Upper Esera has a the Valle de very important. It was possible Since the maximum of the in the karst for the Giiells del the base- velocity water Jueu system, to analyze of system (measured with a tracer) has a value only flow from the depletion curves for the winter months

-1 0.14 m.s the is a superposition of lakes and from December-March 1962—1965. In the winter , system

cascades. Apparently there are narrow tubes in the period the entire Upper Esera area is covered with

3 karst of 20 .s -*. snow and infiltration is at a minimum. system, which permit the passage only m The baseflow

Those narrow tubes must be situated not far under the is characterized by j-values of 30 days, 90 days, 450

3 _1 forats. If of 20 m one is and even 750 This that im- a storage .s during day days days. indicates, an the minimumvolume of the Güells del of the karst reservoir assumed, Jueu portant part empties extremely

6 karst system can be estimated to be at least 1.7 X 10 slowly. The outflow ofthe karst system, even in Febru-

3 -1 m but it is certainly much more. exceeds always 0.3 m*.s This is to a , ary, . equivalent

1 water depth of 0.8 mm.day on the Upper Esera

2 basin (34 km ). Since the total area of the limestones 11.11 into limestones Infiltration 2 of the karst is about 12.7 km the baseflow system ,

-1 Measurements, carried out during July and August of 0.8 mm.day corresponds to an infiltration of 2

1 1965 on karst in the Valle de indicate to De Zeeuw systems Aran, mm.day . According (1966), this type that practically no fast surface runoff is possible on of baseflow can be defined as the seepage flow of the these karstified limestones. baseflow of limestone flow The karst system. The seepage of the Pila karst system areas reached therefore values which exceeded the corresponds with j-values of 30, 50, 100 and 180 days. baseflow little mountain of permeable glaciated high In the Ruda system, j-values of 60, 90 and 240 days basins sandstones and 50 100 for the flow. (granite, slates) by to were computed seepage

12. WATER BALANCE

12.1 Water balance of two selected basins Table 12.1. Water balance of the Pontet de Rius- and Aigües- tortes-basin (1959—1963) The method of Searcy (1960) has been applied for the correlation of the runoff of the Pontet de Rius- Basin and Difference in and the Aigüestortes basin in order to fill gaps the number of Precipitation Runoff Precipitation- records (fig. 12.1). The runoff for both stations (num- gauging (mm) (mm) Runoff ber 20 and has been derived from the recorded 3) station (mm) water stage heights from 1959—1963. The correlation

coefficient has value of 0.90. The annual a average Pontet de Rius

1720 1735 — 15 runoff of stations 20 and 3 amounted to 1735 mm (20)

1560 1643 —83 and 1643 mm respectively. The higher runoff value Aigüestortes (3) of the Pontet de Rius basin is the result of more pre- cipitation (fig. 6.3), which can be evaluated at both 12.2 Water balance of eight basins basins, since their average altitudes are known (fig. 7.4). By using fig. 6.6, precipitation values of 1720 Table 12.2 shows the water balance of eight basins which been in It mm and 1560 mm can be derived. The water balance have analyzed chapter seven. is

(table 12.1) shows errors in the precipitation and clear, that the errors in the terms precipitation and of runoff. The actual evaporation in the Pontet de Rius runoff are significant. Only the water balance the is in the This is and Lower basin greater than Aigüestortes area. Upper Valarties-, Upper Aiguamoix-

due extensive and a show differences between probably to a more scree area Negro-basins precipitation "rouche and which the estimated greater moutonnée" landscape in the Pontet runoff, correspond to evapo-

de Rius basin (fig. 12.2). ration valuesofchapter eight. Precipitation values were 68 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 12.1 Graphical correlation of the runoff of the Pontet de Rius- and Aigüestortes-basin.

with determined fig. 12.3 and fig. 6.6, and runoffvalues the term precipitation minus runoff is too small. derived from tables Valle de were appendix 41, 42, 43 and 44. In chapter 8 the actual evaporation in the

Aran has been estimated to be 500—550 mm (1955 — balance 12.3 Water of the Valle de Aran 1965). If during the years 1962 and 1963, with very balance reliable runoff A water of the Valle de Aran can b: set up data, a precipitation error of ten to for the 1956, 1962 and 1963. those fifteen is assumed, which is due years 1957, During percent very probable the runoff years at station 29, Pont de Rey, is known. to the high position of the rain gauges above ground The runoff data of 1962 and the in the 1963 are very reliable, level, term evaporation water balance (table because have been in the station well with the calculated Pen- they registered power 12.3) corresponds very that of Pont de Rey. man evaporation values. It can be concluded,

The the four estimated the which found in the water precipitation during years was errors, were previous ten values with the method, as explained in chapter 6. The water balances were produced by too low precipitation balance is shown in table 12.3. It indicates, that and inaccurate runoff measurements. Water balance 69

Fig. 12.2 The “roche moutonnée”landscape in the Pontet de Rius basin.

Table 12.2. Ten-year water balance of eight basins (1946— percent of the annual precipitation. During August 1956) and 1956 the free of and September valley was snow,

runoff caracteristics were calculated: 10 % j = 1.5

1 and 15 = 1.5 Basin and Difference day + 2.0 mm day (August) % j

number of Runoff -1 for Precipitation Precipitation- day + 1.5 mm day (September). See also 7.5 runoff gauging (mm) (mm) Runoff runoff characteristics. For the entire Valle de Aran

station (mm) the of the which contributes percentage precipitation, fast runoff the of barren to the corresponds also to area rocks. Iñola (6) 1420 1419 1 de Aran Negro (13) 1790 1672 118 It can be concluded that in the Valle huge which leave the Barrados (16) 1570 1676 —106 quantities ofwater are stored, Upper Garona de after Garonne basin only after six months (snow) or

1450 — 87 Ruda (2) 1537 from Fast run- a period ranging 15—60 days (rain). Upper off is only a minor phenomena. Valarties (20) 1931 1422 509 Upper

1816 1463 353 Aiguamoix (3) Table 12.3. Water balance of the Valle de Aran of 1956, 1957,

Upper 1962 and 1963 Negro (12) 1890 2017 —127 Lower Precipitation Negro (13-12) 1700 1052 648 Precipitation Runoff Year —Runoff (mm) (mm) (mm)

12.4 Runoff of the Valle de Arán 1956 1300 1360 —60

The runoffofthe Valle de Aran (station 29) during the 1957 1120 985 135 calender 1956 is shown in 12.4. The slow 1260 1140 120 year fig. 1962 1963 1650 1400 250 runoff or baseflow is extremely important. It exceeds

1 1.5 mm which corresponds to 30—35 always day , 70 H. Rijckborst: Hydrology of the Upper-Garonne basin

Fig. 12.3 Hypsometric integrals for eight basins.

CONCLUSIONS

1. Therunoff in the Valle de Aran consists essentially 9. The annual actual evaporation (500—550 mm)

of baseflow. decreases with altitude.

2. The baseflow is related to the areas covered by 10. On the glaciers, at an elevation of 3000 m, scree and forest. sublimation exceeds evaporation.

3. Fast runoff is only a minor phenomenon. 11. The storage coefficient of the fast runoff in karst 4. The of the which percentage precipitation con- reach systems decreases rapidly when the systems tributes to the fast runoff is related to the area of the saturation stage. barren rocks.

12. Water infiltrationinto karstified limestones during 5. Orographie precipitation is induced by the slopes trend the snow melt period is highly significant (6 mm/ and general of the mountainranges. day). 6. Broad valleys with steep slopes are characterized

by a homogeneous precipitation pattern. 13. A morphometric analysis demonstrated that the

planation level from elevations 2500—2000 m 7. Rainfall measurements at 1.50 m above ground constitutes the remains of a Miocene landscape, level give about 50 percent higher results than with a relief of at least 1000 meters. those simultaneously recorded from4.40 m above ground level. 14. Specific degradation in a section of the axial zone 8. The Penman of the of the evaporation values give reliable Pyrenees during part Tertiary was results in this mountainous terrain. 33 only mm/1000 year. References 71

Runoff of the de Aran the calendar 1956. Fig. 12.4 entire Valle during year

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La 113. U.S. Weather 1952. of France, p. Bureau, Interpretation missing pre- cipitation records. Monthly Weather Rev. vol. 80 Riesbol, H. S., 1940. Report on exploratory study of rain

shields and enclosures gauge at Coshocton, Ohio. Trans. Vallot, J., 1887. Oscillations des glaciers pyrénéens. Etudes Am. Union, 474—482. 16 Geophys. 21, p. pyrénéennes 3, p. 74 H. Rijckborst: Hydrology of the Upper-Garonne basin

Van Ouwerkerk, J. H. & Pette, D., 1965. Een berekenings- hydrogeology of Navajo Lake, Kane Country, Utah.

methode voor stationaire Geol. Prof. 26 en verzadigde grondwater- Survey Paper 417-C, p.

Kon. Ned. Heide 337— E. 1962. and rain stromingen. Tijdschr. Mij., p. Winter, J., Simple lysimeters unusual

for 348. gauges horticultural research. Special Rept. SR 2,

Williams, G. P., 1963. Evaporation from water, snow and Water Res. Assoc. Div. of D. 1966. ice. Techn. Paper 164 of the Building Research, Zeilmaker, A., Hydrologische en meteorologische

Ottawa. aspecten van het ValledeAran (HogePyreneeën). M.Sc.

M. T. & H. 1964. and Geol. I & 96 40 Wilson, Thomas, E., Hydrology thesis, Inst., Leiden, pt. II, + p. Appendix

TABLES 1 —45 909.4 694.3 898.I 881.I 729.9 89O.I 884.2 979.- 882.I 883.I 922.2 777.- 827.8 981.- year 1112.4 III6.3 IO69.2 1033.- 1050.3

dec. 203.5 IO5.6 12.3 101.3 145.4 89.O 130.6 24.0 122.5 IO7.O 21.0 20.1 110.0 175.0 144.0 30.0 128.O 63.O 94.O 222.0

nor. 11.3 70.2 17.5 201.0 65.2 71.4 19O.O 68.0 39.0 37.5 90.3 83.5 105.6 51.0 82.0 55.0 129.0 80.0 52.0 111.0

1) oct. 39.8 106.0 31.3 46.6 50.0 93.0 112.0 64.0 83.4 72.0 37.0 49.4 46.5 120.0 144.0 111.0 40.0 22.0 II3.O 56.O (st. 22.0 98.4 93.6 78.2 54.8 32.0 70.0 64.2 92.0 52.9 87.O 64.0 76.0 56.0 92.0 Cledes sept. 106.8 164.9 116.0 118.0 117.0 at aug. 137.5 52.O 68.4 48.3 125.9 51.1 63.O 112.3 46.3 87.O 71.0 59.8 90.0 54.O 65.O 33.0 201.0 72.0 48.0 (mm) 79.3 56.O 27.6 40.0 42.0 54.5 July IO6.2 31.0 112.0 II8.0 92.4 13.4 67.O IO5.O 46.0 57.0 IO8.O 36.O 44.0 precipitation june 23.2 76.8 96.3 45.O I29.8 74.O I65.O 54.8 73.4 111.0 199.8 71.0 104.3 65.O 92.0 101.0 99.0 102.0 53.5 44.5 45.O 68.1 92.1 63.0 87.0 69.0 ól.O 92.0 may I27.9 133.6 96.3 47.8 241.6 24.8 142.0 149.0 108.0 104.0 Monthly april 12.0 89.6 59.0 147.0 69.O 86.0 60.5 46.8 20.6 131.4 165.O 76.O 164.0 54.O 96.O 89.O 87.O 77.0 135.O

■arch 30.8 20.8 77-4 56.O 6O.O 50.6 8.5 70.5 20.5 21.0 31.0 I56.O 87.O 65.2 0.1 6O.O IO5.O IO5.O 37.0

Q 8.5 fsbr. 48.5 14. 72.6 84.8 169.5 49.O 71.6 39.0 24.4 31.0 15.2 I3.O 21.0 54.O 74.O 30.0 8O.O I8.O 1. Table jan. 43.3 73-5 34.5 43.0 55.5 83.7 71.5 41.0 142.0 121.5 57.0 33.4 41.8 49.0 85.O 71.0 61.O 40.0 104.8

1 '63 46 %7 V8 '49 50 $1 '52 $3 54 55 •56 '57 '58 59 '60 '61 »52 '64 '65

t 78O.2 846.0 634.7 834.5 800.4 951.6 677.I 865.- 766.5 926.8 801.2 927.9 777.4 858.9 967.3 year II83.I 1041.4 IOI5.5 III5.9 IO65.9

dec. 210.6 I83.O 101.0 34.4 IO7.I 122.6 82.5 123.8 36.9 IO6.O 95.0 19.0 47.7 147.7 103.2 172.I 40.0 97.5 95.0 75.0 177.0

nov. 30.2 23.6 61.O 12.6 142.1 54.8 I7I.5 IO7.2 51.0 48.0 40.7 84.0 62.9 78.7 72.8 95.9 69.6 125.O 137.0 40.5 164.6

2) 29-7 55.3 23.7 41.5 27.5 63.7 oct. 19.8 64.0 85.O 38.O 31.0 59-6 88.0 60.O 67.3 41.0 59.2 111.8 176.4 60.4 102.7 (st. 52.4 44.6 67.8 81.5 82.7 67.O 31.6 75.0 88.0 90.1 45.6 53.1 70.2 72.0 72.0 74.8 Viella sept. 106.8 101.5 103.6 102.6 177.0 at 47.8 71.6 40.6 57.2 65.4 61.6 71.6 62.O 50.O 73.1 74.9 43.6 71.0 25.3 79.0 67.6 aug. 121.5 118.9 IO6.7 247-7 (mm) 25.8 72.8 66.8 60.2 77.0 29.O 86.6 47.O 53.0 81.2 20.7 65.7 77.5 54.5 50.5 44.5 July 105.5 126.9 111.2 IO8.6 precipitation june 85.6 21.8 54.7 96.3 21.7 II8.5 56.4 I77.5 84.0 98.I 77.6 169.8 67.I 71.4 84.5 73.1 28.5 68.5 134.0 52.0 96.4 66.2 27.3 41.3 30.0 28.6 67.4 73.4 62.7 48.5 86.0 84.5 may 174.2 IO7.6 216.5 115.5 171.8 96.2 87.6 49.6 Monthly 15.3 79.9 44.2 44.0 88.6 43.5 44.0 4.0 70.6 66.3 60.I 88.6 84.7 71.6 april I28.6 111.5 117.0 170.4 126.9 120.5

1.0 oh 28.6 69.3 13-0 87.O 54.3 107.2 60.1 14.0 73.0 43.O 44.6 41.5 119.5 111.6 66.2 52.0 50.9 86.2 47.O nar

i 16.6 68.6 11.6 12.1 88.1 68.1 32.4 71.0 32.1 32.6 27.1 38,9 33.0 34.6 26.5 24.1 79.8 40.0 febr. 141.4 101.8

2. 10.4 37.6 94.0 49.7 39.9 98.3 65.0 42.9 60.5 88.4 53.8 58.2 32.5 50.4 85.7 76.5 10.5 76.5 jan. 125.0 101.5 Table '45 •46 »47 »48 '49 '50 '51 '52 '53 '54 '55 '56 '57 '58 '59 '60 •61 •62 '63 '64 '65 839.8 899.5 984.9 936.6 774.6 853.6 year 805.3 661.6 893.9 IO26.8 1272.7 1217.8 793.3 760.4 782.O 809.I 1002.5 1218.5 IIO6.3

dec. I35.6 127.9 21.0 104.3 I89.I 89.O I38.O 48.0 125.O 112.5 13.6 37.3 145.6 II8.3 137.7 32.0 106.I 172.5 77.7 158.7

nov. 26.5 68.3 6.2 I85.5 70.3 I83.I I36.O 81.O 47.7 37.0 56.O 63.I 78.2 49.I 74.9 74.O 112.8 179.6 42.7 114.3

3) oot. 57.5 23.1 46.4 38.2 41.8 68.8 119.5 67.O 48.8 64.0 19.I 48.2 40.5 IO5.4 149.0 IO3.6 40.8 54.5 84.4 45.8 (at. 45.7 58.3 86.8 42.0 36.5 91.2 37.9 35.0 48.1 76.4 71.0 91.0 83.4 Arties aept. II7.5 121.6 104.0 152.2 115.6 109.4 111.2 at 51.2 25.2 87.9 57.4 aug. 71.6 38.I 71.6 83.8 158.O 92.2 93.0 90.5 53.0 II8.0 104.9 80.3 72.4 79.2 221.6 (mm) 96.6 26.7 July 100.0 49.2 59.6 81.7 31.0 122.8 27.4 47.O 68.0 83.0 19.1 76.4 103.1 99.8 46.6 61.3 89.2 precipitation June 16.6 70.6 8O.7 29-8 I28.O 76.O I67.3 94.3 98.O 79.0 I68.9 41.0 80.8 83.6 76.2 122.9 72.0 I62.6 49.3 38.8 58.O 52.0 32.8 69.6 62.8 40.1 42.1 75-8 51.1 54.9 91.9 64.1 may 155.4 100.0 69.2 221.1 101.5 I52.O Monthly 83.9 april 13.8 82.O 41.2 I66.O 45.9 95.3 42.7 39.7 10.0 68.6 111.3 55.9 192.8 56.7 87.0 105.3 103.2 132.0

9.0 39.7 92.2 0.5 76.8 80.6 37.5 march 65.3 14.0 89.0 63.O 125.2 55.0 71.0 44.0 54.O 93.2 83.3 89.7

19.8 60.0 70.0 41.0 26.0 37.1 40.6 30.4 36.6 29.5 91.2 27-9 71.6 37.1 febr. 78.6 17.1 97.9 100.5 200.0

3. 78.0 47.8 46.5 23-9 50.7 79.2 80.5 82.9 13.1 67.6 jan. 51.4 96.7 51.7 43.0 122.1 88.5 54.8 66.4 120.0 Table 49 '45 '46 '47 •48 '50 '51 '52 '53 '54 '55 '56 '57 '58 '59 '60 '61 '62 »63 '64 '65 • Table 4. Monthly precipitation (mm) at Puerto de Bonaigua (st. 4)

jan. febr. march april dec may June July aug. sept. oct. nor. year

'49 44.5 27.4 89.6 68.0 I54.I II5.5 43.5 85.7 I38.2 51.5 205.8 I3I.O 1154.8

'50 54.0 62.3 52.8 176.5 6O.2 44.2 96.I 112.6 114.1

'51 2I8.5 121.0 49.O 152.6 112.1 121.0 200.5 59.5

'52 101.6 155.0 111.5 124.1 57.5 87.O 65.O 109.0 38.5 155.0 I92.O I5O.5 1336.7

'53 74.6 40.0 24.0 71.5 64.5 221.5 44.0 138.O 104.6 98.O 86.0 71.5 IO38.2

'54 39.0 84.5 139.0 IO9.6 202.0 I55.O 88.0 92.5 95.5 83.5 65.O I8O.I 1333.7

'55 94.1 75.1 6I.O 12.0 41.1 I6O.I 91.5 72.O 129.O 175.0 39.2 15^.0 1104.1

'56 216.0 63.0 I26.O I55.O 152.O II6.5 54.0 124.0 134.O 65.O 85.5 23.O 1314.-

'57 99.0 48.0 38.O I88.O 143.0 214.0 47.0 141.0 57.0 68.0 71.0 47.I 1161,-

'58 60.5 35.0 202.0 I54.O 6O.2 92.0 72.0 57.5 44.5 60.5 155.6 179.0 1172.8

'59 36.5 80.0 I8O.O 146.0 99.0 II6.5 87.O 120.0 93.5 125.6 72.0 II5.O 1271.-

'60 96.0 71.0 IO6.O 101.0 65.O I23.O 145.6 82.4 120.4 305.4 137.4 209.0 1562.2

'61 98.0 28.0 4.0 175.O I28.O I65.O 60.6 71.8 78.O 112.5 100.8 49.O 1070.7

'62 102.0 211.0 92.0 110.0 79.0 124.0 36.O 35.0 114.0 69.O 185.0 237.O 1394.-

'63 106.6 69.0 101.0 154.O 97.0 IO5.3 153.0 210.0 121.0 75.0 181.2 86.0 1459.1

'64 35.0 85.0 103.0 110.4 IO3.4 124.2 86.1 76.I 137.3 81.O 93.6 80.0 1113.1

•65 70.7 61.8 57.2 183.6 94.7 62.8 61.0 65.4 171.9 IO6.9 175.2 166.4 1277.6

Table 5. Monthly precipitation (mm) at Benos (st. 5)

arch oct. jan. fotor. n april may juna July aug. sept. nov. dee. year

'55 124.7 62.2 42.0 112.8

'56 89.1 38.5 51.6 78.3 175.5 66.4 65.5 80.5 8o.O 31.4 79.7 19.4 855.9

'57 43.8 37.6 29.7 128.7 85.5 172.7 27.3 64.8 41.6 49.9 70.8 42.4 751.0

'58 74.2 31.6 120.4 76.2 68.0 51.3 58.8 59.5 54.0 55-3 92.5 128.9 87O.7

'59 43.8 20.0 105.7 212.6 79.6 68.5 94.6 72.4 6l.O 126.5 77.6 183.I 1145.4

'60 55.7 26.5 63.2 69.4 48.7 64.8 86.8 46.8 58.0 158.0 IO5.7 121.5 915.1

'61 116.9 38.5 1.5 100.6 74.5 93.3 69.6 55.5 39.0 IO8.7 59.8 31.3 789.2

'62 59.9 66.2 47.2 112.8 44.4 69.0 45.0 16.8 68.6 36.6 125.5 111.7 803.7

'63 37.5 24.2 89.5 89.5 53.1 71.6 85.9 164.9 69.0 25.5 102.5 68.5 881.7

'64 24.0 78.0 88.2 102.5 86.8 92.0 99.1 96.0 85.3 87.7 41.8 98.7 980.I

'65 93.0 31.7 57.5 104.2 83.9 35.3 36.0 66.0 111.8 57.7 137.5 193.0 833.9 6. Table Monthly precipitation (mm) at Camara Barrados (st. 6)

103.0 25.4 '56 80.5 36.6 963.5 128.0 202.4 41.5 92.7 60.9 53.1 '57 56.3 57.8 35.2 138.5 149.9 150.4 1169.3 68.1 74.2 84.6 86.8 62.9 79-3 '58 84.7 57.1 165.2 106.1 190.5 1321.- 110.8 108.5 102.4 68.5 151.0 94.2 '59 68.7 29.0 134.7 168.7 94.0 208.5 1179.3 84.3 98.7 65-0 75-9 177.4 110.2 '60 79.6 30.7 69.7 109.0 70.3 64.1 27.0 1008.8 101.8 135.0 102.9 64.5 50.2 99-4 '61 171.0 57.1 1.5 134.3

56.0 80.0 '62 77.5 148.8 72.8 115.2

at Tunnel Viella North (st. 7) Table 7. Monthly precipitation (mm)

'55 4J.8 179.7 99.4 72.1 116.1 144.7 66.5 182.2

161.2 42.8 '56 155.0 59.1 142.4 159.8 206.1 125.2 140.0 192.7 100.5 27.4 1489.1

87.9 1121.6 '57 52.7 46.5 81.1 148.0 102.4 252.9 34.5 94.1 58.0 70.6 95.1

'58 64.8 79.1 250.4 109.1 97.1 100.5 81.5 158.0 90.1 78.9 88.2 226.5 1385.6

'59 71.5 54.8 282.0 201.0 89.7 121.8 115.0 110.2 87.1 122.5 127.4 150.5 1257.5

'60 115.4 121.6 155.5 81.6 106.5 142.9 157.4 69.5 150.5 541.5 182.0 184.0 1966.-

'61 108.0

Table 8. Monthly precipitation (mm) at Re stanca (st. 8)

oct. dec. jan* feto. march tipril may june July aug. sept. nor. year

'55 I34.7 II8.2 154.7 147.5 88.1 295.2

'56 131.1 76.6 97.3 197.4 140.5 122.9 78.I 228.O 327.9 31.3 87.5 48.3 1566.9

'57 51.2 70.9 75.0 124.4 92.1 259.8 57.0 144.7 77-3 85.O 106.3 72.8 I216.5

'58 77.7 109.7 236.4 129.8 82.9 140.3 91.5 165.8 78.8 102.2 95.2 320.0 I63O.3

'59 38.9 52.3 348.3 264.6 102.4 120.7 I86.6 152.5 94.2 132.5 81,3 139.8 1714.1

'60 175-5 183.7 111.4 73.7 IO7.I 125.2 197.9 119.7 249.2 657.2 178.5 168.2 2347.3

•61 66.0 22.6 2.4 194.I 221.8 153.1 97.4 101.3 122.9 I69.8 164.0 64.5 1379.9

'62 220.9 I26.6 222.5 132.0 63.6 116.1 62.6 54.7 I60.7 97-5 223.3 150.5 1631.O

'63 127.5 73.6 115.3 194.O 67.I 152.8 199.5 327.8 I67.5 8I.3 568.2 80.O 2154.6

'64 31.1 111.0 134.8 180.5 97.0 182.5 183.5 92.0 I85.3 IO6.6 82.I 98.7 1485.1

'65 110.1 63.2 71.6 73.5 92.0 42.6 38.8 31.5 308.4 121.2 220.4 170.2 1343.5 Table 9. Monthly precipitation (mm) at Camara Arties (st. 9)

30.8 69.2 19.8 950.8 '56 34.8 66.9 119.7 137.4 58.5 61.6 132.0 155.4

37.6 64.2 40.5 839.8 '57 69.0 38.4 34.9 118.0 80.2 172.2 16.9 110.4 57.5

46.8 66.8 121.4 856.3 '58 66.9 61.6 104.6 84.3 69-9 54.1 67.8 82.6 29.5

85.0 84.2 89.4 '59 37.1 27.8 150.6 134.1 57.6 81.9 129-5

Table 10. Monthly precipitation (mm) at Moncasau (st. 10)

'55 117.4 129.1 150.8 132.3 78.7 167.7

'56 112.0 81.0 62.3 166.1 117.1 96.0 93.9 193.6 210.9 36.2 113.5 40.8 1323.4

'57 91.5 43.5 44.3 129.6 107.7 241.9 53.8 140.8 54.0 60.4 98.9 73.4 1139.8

'58 99.6 114.1 139-9 119.2 90.3 141.0 93.5 130.2 86.9 93.3 108.1 152.1 1368.2

'59 58.5 29.1 207.2 247.0 92.1 113.6 150.6 122.7 133.2 125.7 66.7 99.3 1429.7

'60 108.1 155.6 88.2 58.2 88.7 183.2 198.4 121.7 186.1 467.1 127.0 157.8 1940.1

»61 59.1 22.8 1.0 140.8

Table 11. Monthly snowfall (cm) at Cledes (st. 1)

winter aept. oct. nov. dec. jan. febr. march april may june july aug. year

'47/48 18 14 1 33

'48/49 24 9 33

8o '49/50 9 26 23 7 15

'50/51

'51/52 6 9 48 55 5 123

'52/53 6 25 60 38 1 130

'53/54 57 13 70

'54/55 10 7 3 20

61 '55/56 2 51 8

'56/57 16 1 47 1 65

'57/58 10 1 9 8 26 2 56

'58/59 8 8

'59/60 2 26 1 29

'60/61 75 21 96

8 '61/62 1 2 29 1 41

'62/63 2 5 1 3 3 1 57

»63/64 3 9 3 15

'64/65 23 22 24 69 Table 12. Monthly snowfall (cm) at Viella (st. 2)

'46/47 63 35 35 135

'47/48 5 5

'48/49 7 7 5 1 20

6 '49/50 30 45 19 3 7 110

'50/51

4 18 42 '51/52 73 2 139

'52/53 21 61 57 38 2 5 l8l

'53/54 12 72 32 3 4 5 128

'54/55 33 12 8 53

'55/56 16 11 45 1 18 7 98

'56/57 20 27 6 49 5 5 107

24 '57/58 3 50 33 30 24 164

'58/59 4 20 4 17 1 1 47

'59/60 4 28 32 2 2 68 182 '60/61 2 80 264 '61/62 20 7 2 8 88 4 23 152

'62/63 13 45 14 16 34 16 138 '63/64 3 10 3 18 9 43 '64/65 3 52 60 49 13 177

Table 13. Monthly snowfall (cm) at Arties (st. 3)

oot. dec. febr. march winter sept. noT. jan. april nay june j»iy aug. year

'52/55 36 70 52 47 3 1 209

'53/54 13 86 51 7 2 8 I65

'5V55 40 10 50

'55/56 3 29 51 5 30 20 138

'56/57 10 61 7 63 11 20 172

'57/58 64 16 82 44 36 44 286

'58/59 13 44 27 33 17 2 136

'59/60 18 3 92 40 11 4 26 194

'60/61 6 182 82 6 276

'61/62 20 17 9 27 117 10 30 1 231

'62/63 5 45 59 32 40 71 8 260

'63/64 8 39 17 7 28 2 101

'64/65 2 ■¿ 11 12 7 5 3 270 Table 14. Monthly snowfall (cm) at Puerto de Bonaigua (st. 4)

410 '48/49 10 5 40 85 28 123 29 33 7

'49/50 82 145 46 79 43 115 4 514

'50/51

646 '51/52 85 88 83 147 120 13 95 15

642 '52/53 16 136 186 135 84 27 26 15 17

'53/54 12 10 73 184 82 89 52 92 594

4 396 '54/55 23 21 63 138 112 35

846 '55/56 12 38 94 158 175 97 136 100 36

144 24 '56/57 42 l6l 34 124 48 25 29 631

180 l4l 4 4 '57/58 32 82 72 117 32 3 707 668 '58/59 16 93 163 59 80 116 129 12

898 '59/60 85 94 283 137 76 105 117 1

12 16 725 •60/61 6 45 72 356 115 17 3 83

266 69 20 765 '61/62 59 57 53 122 90 29

86 857 •62/63 2 36 156 189 101 92 170 25

686 '63/64 3 25 119 131 105 116 142 45

808 '64/65 96 44 179 146 117 75 124 24 3

Table 15. Monthly snowfall (cm) at Benos (st. 5)

winter oct. febr. sept. nov. dec. Jan. march april may june July aug. year

166 '52/53 10 51 66 37 2

'53/54 2 61 28 91

'54/55 10 7 5 22

'55/56 12 17 63 6 98

'56/57 1 29 2 42 5 1 80

9 '57/58 36 4 53 20 20 16 14

'58/59 6 12 9 7 34

' 59/60 32 34 2 68

180 '60/61 110 70

28 '61/62 3 8 2 5 68 114

'62/63 13 40 7 21 24 1 106

'63/64 1 7 7 1 7 23

'64/65 7 2 46 47 49 5 1 157 Table 16. Monthly snowfall (cm) at Camara Barrados (st. 6)

294 '56/57 22 105 15 61 38 53

396 '57/58 94 17 117 58 34 75 1

16 207 '58/59 20 73 29 22 47

46 290 '59/60 40 5 132 10 20 37 284 •60/61 1 16 152 97 18

283 •61/62 20 20 12 37 158 13 20

Table 17. Monthly snowfall (cm) at Tunnel Viella North (st. 7)

274 '56/57 15 91 13 68 42 45

349 '57/58 77 50 87 35 57 53

245 '58/59 26 69 45 45 45 15

264 '59/60 16 11 106 33 29 32 37

317 '60/61 12 142 130 33

Table 18. Monthly snowfall (cm) at Restanca (st. 8)

winter sept. 00t. nor. dec. jan. febr. march »pril may june July äug. year

I88 128 124 10 45 710 '55/56 3 26 115 71

80 26 12 590 '56/57 40 124 54 72 37 145

78 154 18 76O '57/58 23 115 96 124 152

106 3 572 '58/59 2 55 146 70 69 121

96 669 '59/60 55 86 177 103 73 79

260 3 33 13 4 552 '60/61 1 25 48 115 20

84 81 136 10 7 656 '61/62 47 44 54 193

68 114 67 20 700 '62/63 2 12 155 164 98

116 50 532 '63/64 2 10 104 109 51 90

69 42 29 1 655 '64/65 IO8 37 139 140 90 Table 19. Monthly snowfall (cm) at Camara Arties (st. 9)

s * 481* '55/56 92 110 74 95 88 22 12/1^6

'56/57 29 137 40 149 31 7 122 11 7 533

'57/58 20 110 81 137 80 121 100 6 655

'58/59 41 112 82 54 112 100 12 523

Table 20. Monthly snowfall (cm) at Moncasau (st. 10)

'55/56 4 22 122 110 203 65 121 84 44 775

'56/57 56 173 72 144 68 19 164 34 31 761

'57/58 34 132 106 155 125 l60 142 16 86o

'58/59 8 75 153 77 58 124 172 8 675

'59/60 76 62 177 143 119 63 78 2 720

'60/61 5 25 59 267 96 18 1 30 8 509

Table 21. Monthly snowfall (cm) at Bosost (st. 11)

'56/57 1 16 2 44 2 1 66

'57/58 25 1 23 14 31 4 98

'58/59 3 5 2 3 13

'59/60 11 26 1 38

'60/61 93 27 120

'61/62 1 4 37 1 10 55

'62/63 4 40 3 11 20 1 79

'63/64 3 7 6 16

'64/65 26 32 34 2 94 year 10.2 10.2 9.0 3.1 2.2 16.3 16.2 14.0 7.1 6.2 4.0 4.1 3.9 -1.0 -1.9

deo. 3.8 3.1 1.9 -3.5 _3.6 9.0 7.6 5.8 0.2 0.1 1.4 1.4 2.1 -6.7 -7.3 —

nov. 6.5 6.1 4.7 -0.5 -1.4 12.0 11.2 8.9 2.9 2.0 0.9 1.0 0.5 -3.9 -4.8

oct. 11.1 11.0 10.1 4.5 2.8 17.6 17.2 15.3 8.3 6.2 4.6 4.8 4.8 0.6 -0.6 (1955-1965) aept. 15.8 15.2 15.2 9-4 8.1 22.4 22.9 20.9 13.5 12.2 (1955-1965) 9.2 7.4 9.4 5.2 4.0

°C °C

in in (1955-1965) aug. I6.7 I7.5 I6.4 11.0 10.0 23.4 24.7 22.1 15-5 14.5 10.0 10.5 10.6 6.4 5.4

°C July 6.5 5.6 in 17.3 I8.2 I7.O 11.1 10.1 temperatures 23-4 25.0 22.7 15.7 14.6 temperatures 11.1 11.3 11.2

8.6 8.8 9.0 3.9 2.9 june 14.8 15.3 14.2 8.2- 6.9 21.0 21.8 19.4 12.4 10.9 temperatures maximum minimum 5.9 6.1 5.9 9.2 7.3 0.6 0.2 4.9 3.6 18.8 19.3 l6.7 may 12.4 12.7 11.3 _ monthly monthly monthly april 8.7 8.2 6.6 -0.2 -1.3 14.4 13.8 11.3 3.9 2.4 2.9 2.5 1.9 -4.3 -5.1 Average Average Average h 7-7 7.3 5.9 3.2 3.0 1.1 1.2 0.7 maro -1.0 -1.6 14.2 13.4 11.1 -5.2 -6.3

febr. 4.1 3.3 2.0 -4.0 -4.0 10.4 9.3 7.0 0.2 0.5 2.3 2.6 3.1 -8.2 -8.5

Jan. 3.2 2:6 i:8 -3:5 -4:0 8.7 7.6 5.9 0.3 0.3 2.3 2.3 2.4 -7-2 -8.2

23. 24. 22. Table station Cledes Viella Arties Restanca Bonaigua Table Cledes Viella Arties Restanca Bonaigua Table Cledes Viella Arties Restanca Boíiaigua (22$ (21# (23^ (53# (58$

8O.7 76.I 83.7 12.3 12.1 10.1 8.1 8.1 year — O.58 O.7O 1.00 0.73 year 193.8 210.4

9.0 6.5 7.4 O.25 O.58 0.64 0.11 0.59 aug. 1.6 0.8 10.4 7.9 dec.

8.4 6.8 6.8 0.14 0.68 O.62 1.00 0.65 0.7 0.7 ll.l 10.2 nov. (1955-1965) July

7-7 6.8 0.04 0.53 0.60 4.2 6.1 13.0 12.4 10.5 oot. I.89 O.78 june (1955-1965) below

(1955-1965) m 8.3 8.2 - O.69 I.45 O.76 0.4 0.4 0.3 13.2 15.5 11.5 sept. 0.21 may 11.3 15.7 °C in 9.1 9.1 0.53 0.64 1.11 temperatures 2.9 4.8 5.6 13.4 14.2 11.5 aug. O.28 O.69 april 24.9 26.8

h amplitudes 9.2 9.0 gradiente July O.58 O.70 1.22 O.74 9.1 8.7 9.7 12.3 13.7 11.5 -0.32 minima maro 27.0 29.2

8.5 8.0 with 12.4 13.0 10.4 june -O.18 0.53 O.7I I.45 O.78 oor. 18.5 17.1 17.9 26.2 27.3 f temperature 8.6 7.5 temperature days, 12.9 13-2 10.8 may 0.68 O.76 I.45 O.82 _0.11 Jan. 19.5 l8.3 18.9 28.7 30.6 monthly monthly frost 9.4 8.2 7-5 of 11.1 11.3 april O.I8 O.78 O.8O 1.00 0.84 dec. 17.7 15.3 17.8 28.7 29.6 Average Average number 8.4 9.3 0.14 0.68 0.82 0.89 0.80 13.1 12.2 10.4 march nov. 11.0 10.0 11.1 23.6 26.0 monthly

O.28 O.63 O.7I — 0.64 10.1 8.4 9.0 febr. oot. 1.6 1.5 2.4 12.7 14.7 12.7 11.9 Average in °C/100 0.21 0.39 0.63 O.56 0.62 4.2 2.9 9.9 8.3 7-5 8.5 jan. 0°C sept. 11.0

25. 26.

27. Table Cledes Viella Arties Restanca Bonaigua Table station Table CledesAiella Viella/Arties Arties/Rest. Rest./Bon. Arties/Bon. station Cledes Vlella Arties Restanca Bonaigua 3.7 5.7 10.0 61.6 71.0 (35.0*) (36,2*) (37,4*) (4l,2*) (39,6*)

year 127.8 131.9 136.4 150.3 144.8 10.3 19.5 28.2 66.1 72.4

dao. (1955-1965) 11.3 12.3 13.6 13-7 13.7 2.9 4.6 6.3 11.7 11.8 nor. 0.6 1.5 3.1 8.1 8.6 °C 0.1 0.2 11.3 11.9 11.8 12.1 13.1

0

below oct. 9.1 9.8 0.1 0.5 0.8 3.4 4.6 0.4 1.7 10.3 11.6 11.1

•

aapt. 0.2 0.4 temperatures 5.9 9.7 10.0 10.3 11.3 12.4 11.3 (1955-1965) aug. 9.2 9.9 9.8 0.1 0.3 0.7 7.2 7.5 10.0 10.9 maximum days 0.1 9.9 9.2 (1955-1965) 3.8 July 10.1 11.8 10.1 with 1.4 2.1 12.2 13.2 days june 12.2 0.9 1.5 1.3 1.8 2.6 13.2 12.4 12.1 12.0 15.1 13.4 precipitation snow

may of 0.1 0.5 0.2 2.4 3.3 0.9 1.5 2.5 13.7 13.2 of 11.7 11.1 11.3 12.8 11.7 number number number 0.6 1.8 2.6 0.3 6.6 9.3 april 15-7 15.6 15.0 15.6 16.0 10.3 12.0

monthly monthly h monthly 9.8 1.1 1.9 3.4 9.7 2.1 3.7 maro 10.8 11.5 12.9 12.5 10.1 Average Average Average febr. 2.2 4.5 5.2 9.3 oficeys, da 0.2 0.1 7.3 7.9 8.6 9.9 10.0 9.1

Jan. 10.3 11.0 10.9 11.5 12.1 2.7 4.2 6.6 10.3 10.7

28. 29. 30. Table Table station Table Cledes Viella Arties Restanca Bonaigua Cledes Viella Arties Restanca Bonaigua Cledes Viella Arties Restanca Bonalgua year 44 46 47 46 48 159.I 155.7 152.8 I61.I 135.0 118.3 133.0 134.7 130.5 106.5 87.6 76.3 77.6 73.4 123-5

5.8 5.1 3.8 3.5 6.6 deo. 45 52 49 47 51 14.3 12.5 13.9 14.6 12.4 10.9 13.4 13.3 12.9 12.0

9.6 7.4 5.8 6.4 6.3 8.2 nor. 44 48 49 48 54 13.I 12.6 12.1 12.6 10.2 11.6 11.5 11.1 11.6

8.2 9.8 9.7 7.5 6.2 6.0 5.3 9.8 oot. 57 41 45 44 50 15.3 15.0 14.2 14.7 11.5 10.8 10.8

1955-1965 13.0 10.2 1955-1965 9.3 9.6 7-3 1955-1965 8.0 7.0 6.8 7.0 ■ept. 45 42 46 45 48 13.6 13.4 12.7 10.5 10.0 12.5

8.4 9.6 8.9 5-2 9.0 6.5 6.7 7.8 aug. 59 13.6 14.9 14.1 14.3 13.5 10.2 12.3 (1955-1965) 42 41 44 41 (0-1/10) (9/10-10/10) (1/10-9/10) days 9.4 5.8 8.0 6.0 7-3 7-5 59 13.6 13.8 July 47 45 44 42 12.1 14.1 14.1 10.9 10.9 10.1 days 11.4 days percentage cloudless 10.8 11.8 11.2 13.2 11.1 10.1 10.7 10.2 9.2 6.6 9.1 7.5 8.6 7.6 12.3 june 47 48 48 45 45 clouded clouded la of of of 7.4 9.6 9.4 9.3 47 46 49 50 49 11.1 11.0 11.0 11.0 10.4 10.3 10.0 10.6 10.7 10.0 12.2 cover may number number number 8.8 7.1 7.7 8.8 7.4 7.6 7.2 7.4 6.3 cloud 58 64 62 60 59 13.6 15.7 14.9 14.9 11.4 11.2 april monthly monthly monthly 8.4 9.5 6.9 6.4 7.0 5.8 monthly 54 14.6 13.8 12.0 12.4 10.8 12.0 12.8 10.9 11.7 naroh 42 46 50 51 Average Average Average 8.3 9.0 9.7 9.5 8.3 4.5 4.5 4.3 3.5 7.9 Average 40 15.2 14.5 14.0 15.O 11.8 febr. 58 45 41 45

9.2 4.3 4.1 3.8 3.3 6.4 59 44 17.5 15.0 I6.3 I7.4 14.3 11.9 10.9 10.3 10.3 jan. 57 45 41 32. 34. 33 31. Table Table Restanca Bonaigua Restanca Bonaigua Table Bonaigua Table station Cledes Viella Arties Cledes Viella Arties Cledes Viella Arties Restanca Cledes Viella Arties Restanca Bonaigua year 0.8 102.8 99.3 26.3 88.0 194.6 138.1 217.3 58.5 133.4 82.9 120.5 5. 215.9 20.7

dec. 6.7 6.1 2.1 7.6 18.8 0.2 11.8 19.9 5.6 11.0 9.7 12.1 0.6 17.6 0.5

5.9 6.9 2.3 8.3 17.4 0.1 4.2 9.8 8.7 1.9 nor. 11.2 19.8 11.0 17.3

8.5 7.4 2.7 8.3 15.3 0.1 4.7 6.7 0.4 2.5 oot. 12.1 18.6 12.5 10.6 17.8

9.2 8.1 1.7 3.8 0.3 5.6 (1955-1965) sept. 14.1 (1955-1965) 11.0 16.3 11.6 (1955-1965) 5.9 9.9 0.9 20.3 2.7 2.1 5.6 winds aug. 11.0 11.4 15.1 10.9 17.4 5-3 11.9 4.5 8.5 0.7 20.0 2.6 winds winds 7-3 July 11.5 12.4 1.9 15-0 17.4 7.0 11.2 3.8 6.2 0.2 3.1 northern eastern 12.0 southern 16.6

with 9.4 9.6 3.2 5.5 15.7 5.8 4.2 8.7 0.7 1.5 june with 11.2 16.1 11.2 with 18.4 days days days 9.1 8.8 3.2 8.1 5.4 of 17.4 16.4 4.3 7.9 0.2 1.8 may of 13.6 10.9 of 17.7 number 9.7 2.4 12.1 18.8 number 3.1 8.7 number 4.8 7.9 0.1 1.4 april 10.2 12.0 13.9 14.2

monthly h 7.7 6.5 1.8 7.4 l6.l monthly 12.3 19.9 3.2 13.0 monthly 9.2 0.6 0.8 maro 11.9 20.3

Average 2 6.6 5.6 1.7 5.8 Average 4.8 Average 9.7 0.3 0.8 febr. 16. 10.6 19.9 10.5 11.8 17.4

7.0 6.8 1.2 8.2 17.7 0.1 9.4 21.7 4.2 11.1 11.4 14.0 0.3 l8.3 1.1 jan.

35. 36. 37. lia

station e Table Cledes Viella Arties Restanca Bonaigua Cledes Arties Restanca Bonaigua Table Cledes Viella Arties Restanca Bonaigua Table Vi year 174.6 7.1 113.4 0.8 10.5 2.9 3*4 1.8 3.0

deo. 8.1 14.0 0.9 0.2 0.4 0.3 0.2 0.5 I dec. 2,8 2,8 2,8 4,3 3,8 0.9 7.8 0.1 0.6 0.3 nor. 15.0 0.3 0.2 0.1 nov. 2,7 2,7 2,7 4,2 3,5 965. 0.8 8.9 0.7 0.2 0.4 0.2 2,3 2,3 2,3 3,8 3,2 oot. 15.5 (1955-1965) 1955—1 okt. (1955-1965) aept. 14.5 0.9 10.9 0.1 1.5 0.2 0.2 0.2 0.1 period aept. 2,0 2,0 2,0 3,5 2,8 2,0 2,0 2,0 3,6 2,7 the aug. aug. 0.5 1.3 0.4 0.1 0.1 winds 15.4 10.3 wind-direction during Juli 1,8 1,8 1,8 3,3 2,8 western duly 15.2 0.4 11.6 1.2 unknown 0.4 0.3 0.1 0.5 (U2) juni 1,7 1,7 1,7 3,1 2,7

with 0.5 9-7 0.1 1.5 with 0.3 0.2 0.1 June 16.2 0.1 mei 1,8 1,8 1,8 3,3 3,0 days days velocity 2,5 2,5 2,5 3,9 3,6 of 0.6 0.1 0.7 of 0.3 0.3 0.1 0.2 april may 17.2 10.8 wind number number maart 2,8 2,8 2,8 4,3 3,9 april 14.9 0.4 13.3 0.2 1.0 0.2 0.2 0.4 0.1 monthly monthly monthly febr. 3,0 3,0 3,0 4,5 4,5 march 13.6 0.2 8.6 1.0 0.5 0.2 0.1 0.1 Average Average Average jan. 3,1 3,1 3,1 4,7 4,1 0.2 6.0 0.4 0.2 0.3 0.3 febr. 10.8 40. Table Station Cledes Viella Arties Restanca Bonaigua 0,8 7.4 0.2 0.4 0.2 0.3 0.1 0.7 jan» 12.5

38. 39. Table station Cledes Viella Arties Restanca Bonaigua Table Cledes Viella Arties Restanca Bonaigua - - year 1313 151O 1772 2093 1684 1220 1241 957 1419 1232 1397 940 1810 1988 241? 2012 I585 1463 1927 1676

- 40 82 92 76 78 98 48 58 82 aug. I65 64 58 56 76 185 88 97 65 65 129 88

- 72 49 July IO8 52 140 197 118 87 90 101 93 64 96 16) 103 152 242 149 179 162 265 151

6)

- 128 126 115 217 (st. 87 (st. june I65 332 391 356 291 236 217 204 323 460 343 353 323 136 407 285

- river river may 271 166 544 366 390 544 24? II8 287 326 311 288 134 362 324 454 424 359 243 357 314

- Iñola 76 64 april 214 157 239 339 146 143 240 198 Barrados 172 114 153 176 189 404 187 135 182 110 182

the - the 45 83 53 27 75 62 of march 158 126 262 115 113 109 137 97 71 of 132 125 236 125 100 116 (mm) - 50 25 61 57 68 40 46 54 25 47 (mm) 47 febr. 77 25 91 79 157 84 63 101 59 78 runoff - 58 29 64 80 72 51 35 41 62 runoff jan. 127 53 82 47 93 85 99 90 55 146 96 84

- monthly dec. 39 56 31 38 79 85 50 58 73 216 monthly 48 75 53 144 90 112 142 59 145 87 95

- nor. 32 39 50 94 51 35 79 Average 107 168 139 Average 45 114 63 148 l60 172 131 130 84 90 114

- 22 86 23 55 82 98 92 69 45 63 oct. 47 101 67 58 6l 107 m-7 77 85 149 90 41. 42. "

- sept. 31 35 81 83 55 45 78 51 63 50 54 55 88 53 57 83 79 Table 105 Table 129 112 107 1947 1948 1949 1950 1951 1952 1955 1954 1955 1956 19*7 1948 19*9 1950 1951 1952 1953 1954 1955 1956 Table 43. Average monthly runoff (mm) of the Negro river (st. 13)

febr. march sept. 00t. nor. deo. jan. april may juno July aug. year

1947 85 83 65 82 66 69 173 119 251 153 90 78 1314

1948 71 79 76 82 92 83 81 121 297 242 148 79 1454

84 1949 112 79 62 68 74 50 70 91 98 123 70 981

1950 84 73 126 103 69 59 79 107 294 I63 77 69 1303

1951 82 76 118 74 95 82 176 219 36O 486 321 274 2363

1952 187 168 223 136 119 117 193 295 369 335 206 121 2469

182 1953 124 147 198 221 93 57 76 134 212 199 77 1720

1954 80 84 88 89 93 85 119 136 274 312 249 I65 1784

1955 152 120 103 116 121 86 107 lol 184 194 112 68 1524

1956 79 124 116 125 150 102 118 157 316 193 191 l4l 1812

106 103 117 109 97 79 119 I54 266 240 166 114 1672

of the river Table 44. Average monthly runoff (mm) Garona de Ruda (st. 2)

954 1947 58 58 61 60 57 48 112 144 132 97 73 54

1948 48 56 54 53 52 47 71 91 123 35 87 64 831

1949 75 65 49 60 65 57 66 89 114 131 78 89 938

284 26l 121 1950 95 78 81 86 82 68 95 113 133 1497

240 246 1957 1951 97 80 122 89 8o 69 l4l 193 430 I70

87 1689 1952 147 139 206 115 8l 85 106 168 199 223 133

1955 95 134 104 109 78 60 73 121 201 177 139 102 1393

1471 1954 85 93 89 111 65 54 69 98 2l6 295 204 92

88 82 1955 83 75 76 94 97 78 96 133 198 123 1223

299 182 1956 82 91 80 98 78 63 70 96 276 117 1532

98 99 108 100 80 68 93 132 234 255 160 110 1537 Table 45.

maand Precipi tation in mm c f the st

statior s: Viella Cledes Arties Bonai^ua Restanca Cledes Viella Arties Bonaigua Restanca

66 66 83 103 jan. 67 0,86 0,88 0,85 0,80 0,71

febr. 48 51 62 75 89 0.64 0.68 0.79 0.71 0.61 mrt 60 66 141 . 56 94 0,73 0,81 0,85 0,90 0,98 apr. 88 76 81 127 156 1,14 1,02 1,04 1,22 1,07 mei 95 86 81 107 107 1,23 1,15 1,04 1,02 0,73

juni 91 82 89 126 142 1,18 1,09 1,14 1,21 0,98

68 juli 65 71 75 132 0,85 0,94 0,87 0,72 0,91

aug. 78 79 87 103 154 1,02 1,06 1,11 0,88 1,06

83 80 82 106 sept . 173 1,07 1,07 1,05 1,01 1,19 okt 64 63 110 173 . 72 0,93 0,86 0,81 1,05 1,19 nov. 81 82 84 128 189 1,05 1,10 1,08 1,22 1,30 dec. 102 100 107 121 161 hll h}} llll 1,21 1,10

jaar- totaal 925 897 937 255 17201

maand- gem. 77 I ? 5 78 105 145 1,- 1,- 1,- 1f- 1,-