FRIEND: Flow Regimes from International Experimental and Network Data (Proceedings of the Braunschwei] Conference, October 1993). IAHS Publ. no. 221, 1994.

Impact of large-scale amelioration on the hydrological regime of Belarusian Polessye rivers

B. V. FASHCHEVSKY Central Research Institute of Complex Water Resources Use, Minsk 220086, Republic of

Abstract Studies of man's impact (amelioration activities accompanied by the creation of reservoirs, straightening and diking of channels, intensified agricultural production, etc.) on qualitative and quantitative indices of the river regime have been performed. Specific quantitative changes in the characteristics of annual, maximum and minimum flows, in slopes and tortuosity, as well as the hydrochemical parameters (pH, BOD5, COD, 02, CI, S04, N02, HC03, phenols, oil products, surfac­ tants, heavy metal salts), over many years are described here.

INTRODUCTION

Large-scale amelioration activities such as the construction of open drains, dense drainage networks, lockage systems and reservoirs, river channel straightening and diking, as well the increased amounts of mineral fertilizers and pesticides applied on the newly-developed lands of Belarusian Polessye have caused critical changes in the hydrological (hydrochemical, thermal, etc.) regime of the rivers. A great number of papers e.g. Bulavko (1971), Drozd (1984), Shebeko (1983), Moklyak (1973), Karkutsiev (1982) and others are devoted to the problems of amelioration effects on the rivers of Polessye as a whole, including the areas both of Belarus and the . For years, these problems have led to contradictions among scientists due to the directly opposite results of amelioration effects. The problem is that various natural conditions (marshlands, underlying soils, terrains, soil moisture, etc.) and even amelioration works (open drains and closed drainage, lockage, deepening and straightening of channel, etc.) have often been ignored.

CHANGES OF THE WATER REGIME

Several techniques have been applied to estimate the modifications to flow charac­ teristics under amelioration effects: - by relationships with the flow-forming factors (precipitation, snowpack, air and soil temperatures); - by relationships with the analogous river flow unaffected by amelioration activities; - by fitting probability curves of flow characteristics preceding and following the amelioration activities (provided long-term records are available). The coefficients of annual, minimum and maximum flow changes as well as those of flood-plain duration and height are given in Table 1. The data analysis shows that, in general, the annual flow values at the majority of rivers are increased, except River 214 B. V. Fashchevsky

Table 1 Changes of annual, minimum and maximum flows characteristic of Belarusian Polessye rivers.

River - point Catchment Coefficients discharge change in the years of different frequency: area (krr annual minimum maximum submersion of flood- mean plain

50% 50% 50% 5% duration height

Yaselda — Beryoza 1040 1.30 1.30 0.90 0.92 0.68 0.82

Yaselda - Lenin 5110 1.40 1.80 1.40 1.50 1.29 1.34

Bonrik — Parohonsk 1450 1.10 1.60 0.92 0.90 - -

Tsna — Dyatlovichy 1100 1.45 2.15 2.00 1.50 1.45 1.08 Goryn — Rechitsa 27000 1.35 1.60 - - - - — Novodvortsy 813 1.15 1.25 1.20 1.20 - - Sluch — Starobyn 1780 0.80 0.95 0.55 0.45 0.56 1.04 Ubort — Krasnoberezee 5260 1.20 1.25 - - - - Pytch — Luchytsy 8770 1.25 1.30 - - - -

Oressa — Verhutyno 520 1.25 2.40 0.85 0.75 0.76 0.88

Oressa — Luban 1290 1.15 1.80 0.45 0.50 0.09 0.11 Vyt — Borysovshyna 782 1.35 3.20 1.30 1.20 - - Slovechna — Kuzmychy914 1.20 1.70 - - - - Cherten — Nekrashevka 420 1.20 1.70 - - - - Kopaywka — Chersk 382 1.35 2.10 - - - - Lan — Loktyshy 909 1.00 1.60 1.16 1.10 0.94 0.94

Pulva — Vysokoe 317 1.20 1.50 2.20 - - -

Sluch, downstream of the Soligorsk Reservoir. Here, the extra evaporation losses and great amounts of water utilized at the integrated potassium plants and other industries result in flow reductions to below normal. The annual flow at River Lan, near the town of Loktyshy remains unchanged. Changes of spring flood maximum values preceding and following the amelioration activities are characterized both by their decrease (Yaselda-Beryoza, Bobrik-Harohonsk, Sluch-Starobyn, Ptych Luchytsy, Oressa-Luban, Oressa-Verhutyno) and increase (Yaselda-Senin, Tsna-Dyatlovychy, Sluch-Novod- vortsy, Vyt-Borisovhyna, Lan-Loktyshy, Pulva-Vysokoe). The spring flood maximum reduction can be explained by the enlarged depth of the aerated soil layer, channel straightening, changes in the river network density, reservoir maximum relief, etc. The Luban and Soligorsk Reservoirs are typical of situations where the floods downstream of the control section are reduced to half the natural maximum amplitude. It is interesting to note that on River Yaselda at the two control sections different amelioration effects on maximum flows are observed. Upstream of the town of Beroyza, drainage systems and Selets Reservoir have been built causing some reduction of the Impact of large-scale amelioration on the hydrological regime ofBelarusian Polessye rivers 215 maximum (by 10%). At the lower reaches, upstream of Senin Village, the maximum water flows are increased due to River Yaselda's main channel embankment and cutting off the flood-plain. In general, the hydrographical changes of the Polessye river network which influence the maximum's formation and changes, should be considered in more detail. In the basin (including the areas of both Belarus and the Ukraine) the open canal network density is increased more than twofold - from 0.32 km km"2 to 0.68 km km"2. Taking into account the closed drainage, it amounts to 1.61 km km"2, being five times as large as natural drainage indices. The more striking examples of the canal network density changes are observed on small streams. On River Yaselda (near Senin) the network density is increased by a factor of 7.7, and taking account of the closed drainage by a factor of 26. The density of the open canal network at River Bobrik is increased by a factor of 5 and taking account of the closed drainage by a factor of 10. In general, the small streams of Belarusian Polessye are characterized by the open canal network density increase by a factor of 2-3, and taking account of the drainage network by a factor of 5-10. The river channel straightening leads to changes of tortuosity, length reduction and stream slopes increase. As seen from Table 2, the slopes essentially increase amounting to 20-60%. Likewise, the tortuosity correspondingly declines. The character of flood-plain inundation significantly changes during spring floods. On the rivers with declined maximums, the inundation duration and water height on the flood-plain decrease. This is evident on the rivers which have been regulated by reservoirs (River Sluch, near Starobyn and River Oressa, near Luban). It should be noted that near Starobyn, the inundation height remains unchanged, and even rises to some extent. Meanwhile the water stage duration on the flood-plain is halved. The flood-plain at River Oressa near Luban is no longer flooded (water height and duration decreased by 90%). As a result, the conditions are impaired for fish spawning and growth, meadow plant reproduction, etc. On the rivers with increased maximum the inundation duration and water height increase (rivers Yaselda, Bobrik), but at lesser degree than the maximums. On most of the rivers, the minimal daily winter discharges have increased by a half or doubled due to an increase in storage capacity, when water is accumulated in warm periods and used in winter. The minimal discharges have declined at Starobyn (to zero) resulting from the regulation of the Soligorsk Reservoir regime.

Table 2 Changes of slopes and tortuosity at river reaches after regulation.

River Length of Slope % Coefficient; Tortuosity: Coefficient straightened before after of change of changes reach (km) regulation regulation natural straightened channel channel Tsna 1.6-65.5 0.232 0.367 1.58 1.37 1.12 1.22 Bobrik 30-56 0.219 0.266 1.22 1.29 1.06 1.29 Lan 25-76 0.239 0.378 1.58 1.63 1.03 1.58 Moroch 13.5-27.5 0.264 0.336 1.27 1.31 1.026 1.28 216 B. V. Fashchevsky

CHANGES OF THE HYDROCHEMICAL REGIME

To estimate the anthropogenic effects on the hydrochemical regime of the Belarusian Polessye rivers, a comparative analysis is made of the natural (background) and current conditions with almost similar water availability at various phases of the water regime (spring flood, summer and winter low flows). The results of studies by Sivko (1956) are applied as background data obtained for the summer low-flow period of 1953. The results to be compared with are taken for the 1980 (1981, 1984, 1985, 1986, 1987) periods of similar water availability. Besides, data provided by the Belarusian Hydrometeorological Survey for the period preceding the intensive amelioration activities (1952-1962) and following the large-scale economic development of the Polessye Region (1981-1988) are considered. The comparative analysis indicates that pH remains unchanged in the summer low flow period independent of the intensive economic activities on most of the rivers concerned (rivers Pina, Bobrik, Lan, Sluch, Moroch, etc.). The dissolved oxygen content increased by 20-30 % as compared to that of the natural regime, owing to improved water aeration on the works and, sometimes, to complete disappearance of peatlands in the river basins. The contents of slightly oxidated organic matter abruptly increased. Thus, BOD5 on the River Pina, near Pinsk increased by a factor of 3.3, on the River Lan, near Mokrovo by a factor of 2.2, on the River Sluch by a factor of 2, on the River Oressa, near Andreyevka by a factor of 3, etc. As a whole,the growth of BOD5 reflects the intensive anthropogenic pollution of rivers with organic materials. On the contrary, chemical oxygen demand (COD) characterized by bichromaticoxidation is diminished on several streams due to reduced inflow of marshland waters which have been loaded with humin materials resulting from amelioration activities. A fast growth of chloride content is found to be typical for river waters of Polessye. The average growth amounts to 200- 300% with some rivers exceeding these figures (on River Sluch by a factor of 5-6, on the River Moroch by a factor of 11). A fast growth of sulphates is also observed, increasing the average by a factor of 5, in some cases reaching a factor of 10-20 as compared to the data of 1953. A slight growth of calcium by 10-20% as compared to the natural regime should also be mentioned. Due to the reduced inflow of marshland water, iron content is decreased in most rivers during a summer low flow. The comparative analysis of the dissolved solids content in different phases of the water regime (winter and summer low flow, a flood preceding the intensive amelioration activities in 1952-1962 and following them in 1981- 1988) reflects a picture described below. The dissolved oxygen content increases to some extent (by 10-20%) or remains unchanged. pH remains the same, though in the riversflowin g from reservoirs and lakes a tendency is seen to alkaline reactions. In all the water regime phases, the growth of chloride content by a factor of 2-3 (from 2-5 mg I4 to 10-20 mg l"1) and nitrates by a factor of 5-10 (from 0-0.5 mg l"1 to 0.10-1.0 mg l"1) is observed. However, when the Soligorsk Reservoir was built, nitrate content abruptly decreased (by a factor of 2-3) as a result of nitrate accumulation and absorption by the reservoir aquatic plants in River Sluch, near Starobin. Phosphates content is left practically unchanged in most of the rivers, but not all (Rivers Oressa, Goryn, Ubort). General mineralization is found in all the rivers (see Table 1), especially during a spring flood (by a factor of 2-3). It should be noted that general mineralization is caused, primarily, by hydrocarbonates (HC03) Impact of large-scale amelioration on the hydrological regime of Belarusian Polessye rivers 217

as well as by an increase in calcium, manganese, sulphates, nitrates, etc. In recent years, such specific pollutants as phenols, oil products, surfactants, heavy metals, salts, etc. are essential for the ecology of streams and lakes. The analysis is made on the basis of data obtained in 1991 at different phases of the water regime taking into account the fact that these substances go over sanitary and fishery maximum

Table 3 The characteristics of MAC exceeding pollutants of Polessye rivers in 1991.

River — point Pollutants Spring flood: Summer low-water: Winter low-water: mg l"1 factor of mg l"1 factor of mg l"1 factor of exceeding exceeding exceeding MAC MAC MAC Yaselda — Beryoza 1 0.019 19 0.013 13 0.008 8 2 0.82 16.4 2.75 55 0.05 1 3 0.056 0.56 0.05 0.5 0.043 0.4 4 0.16 8 0.02 1.0 0.0 0.0 5 0.23 0.46 0.26 0.52 0.24 0.48 7 0.036 36 0.003 3 0.005 5

Goryn — Rechitsa 1 0.010 10 0.06 6 0.03 3 2 0.06 1.2 0.70 14 0.05 1.8 3 0.04 0.4 0.06 0.6 0.005 0.05 4 0.076 3.8 0.05 2.5 0.02 1.0 5 0.05 0.10 0.07 0.44 0.05 0.1 6 0.004 4 0.003 3 0.005 5 7 0.006 0.6 0.005 0.5 0.006 0.6

Sluch - Starobyn 1 0.009 8 0.044 4.4 0.004 4 2 0.05 1.0 0.07 1.4 0.03 0.6 3 0.06 0.6 0.04 0.4 0.02 0.2 4 0.06 3 0.03 1.5 0.0 0.0 5 0.02 0.04 0.07 0.74 0.10 0.20 6 0.003 3 0.002 2 0.003 3 7 0.003 0.3 0.003 0.3 0.003 0.3

Ubort - 1 0.016 16 0.02 20 0.005 5 Krasnoberezee 2 0.9 3.8 0.43 8.6 0.0 0.0 3 0.03 0.3 0.08 0.8 0.005 0.05 4 0.036 1.8 0.031 1.5 0.021 1.4 5 0.63 1.26 0.25 0.5 0.22 0.44 6 0.003 3 0.002 2 0.002 2 7 0.002 0.2 0.003 0.3 0.004 0.4 Pytch — Luchytsy 1 0.033 33 0.03 30 0.03 30 2 0.6 12 0.32 6.4 0.21 4.2 3 0.01 0.1 0.06 0.6 0.03 0.3 4 0.048 2.4 0.031 1.5 0.028 1.4 5 0.51 1.02 0.06 0.12 0.16 0.32 6 0.003 3 0.004 4 0.001 1.0 7 0.003 0.3 0.005 0.5 0.003 0.3

Pina - Pinsk 2 0.06 1.2 0.60 12 0.12 2.4 3 0.025 0.25 0.05 0.5 0.03 0.3 4 0.056 2.8 0.027 1.35 0.027 1.35 5 0.32 0.64 0.20 0.40 0.18 0.36 6 0.006 6 0.004 4 0.007 7 7 0.007 0.7 0.006 0.6 0.007 0.7 * note: 1 — phenols; 2 — oil products; 3 — surfactants; 4 — nitrites; 5 — iron; 6 — copper; 7 — nickel 218 5. V. Fashchevsky admissible concentrations (MAC). The background values of these indices for the past years are lacking since the analysis has not been made. As is seen from Table 3 the MAC levels of phenols are exceeded by 3-30 times in all the rivers (except River Pina for which the data are not available). Oil products concentrations are only not exceeded in five cases out of 18. The MAC are not exceeded with respect to the surfactants. The carcinogenic nitrite concentrations are only not exceeded in four cases out of 18. On the contrary, the iron concentrations are slightly exceeded only in two cases out of 18. The high copper contents can hardly be explained in the rivers of Polessye. Probably, copper additives in mineral fertilizers applied for crop growth on ameliorated peatlands cause an increase in copper contents of the river water. The MAC levels of copper are increased by 2-30 times in 17 cases of 18. On the contrary, nickel concentrations are within the established limits in 17 cases out of 18. A probabilistic and statistical analysis is also made by fitting frequency curves

\ \ 1.0 \ OS V 0 6 \ \ 04 \ 3.0! Y \ \ \ 2.0 0.2 ^V v. \ 1.0 0.1 V \ "V Ov. 0.5 00'S — -\ ^v*». \ IT **» 0 0' \ 1 0.1 001 \ 1 \ 1 0.05 — "^

"•—~ *"-— 1 1 0.01 1 i 10 30 50 SO 90 95 98

Frequency, %

— — — spring

summer

winter MAC Maximum of admissible concentrations Fig. 1 Curves of frequency of oil product concentrations in different seasons for the River Jaselda near Beryoza. Impact of large-scale amelioration on the hydrological regime of Belarusian Polessye rivers 219

indicating the above-mentioned indices in different phases of the water regime for a long time period. It is illustrated in Fig. 1 where the frequency curves of oil products content in the River Yaselda, near Beryoza, are fitted for different seasons (spring, summer, winter). The analysis shows that MAC levels are exceeded 75-80% of the time in the river water. As a whole, similar data exists for oil. The MAC levels of phenols are exceeded 60% of the time. The picture of copper content is more morbid: MAC levels are exceeded in 90-95%, or only during 5-10 years out of 100 years is the exceedance of copper contents not observed. Research work by Vinberg (1956) comparing the eco­ logical parameters of Chervonoye Lake of 1956 and the data of 1905 shows no changes for 50 years. The comparisons made by the author for the last 30-35 years indicate that the river and lake ecosystems of Belarusian Polessye have been damaged, particularly Chervonoye Lake. The large-scale economic development of the river systems, paying no regard to the ecological situation, has caused adverse effects.

REFERENCES

Bulavko, A. G. (1971) Vodny Balans Rechnych Vo&wfeorov (The water balance of river basins). Drozd, V. V. (1984) Mezhenny stok meliororovannychvodosborov(The low flow of ameliorated watersheds). Problem) Polessja, N9, 85-90. Fashchevsky, B. V., Avsievich, L. V., Pochodnia, G. V. & Talaluiev, V. G. (1991) Ecologicheskayaotsenkavodnogo rezhima rek i ozyor Polessia (The ecological estimation of changes in the water regime of rivers and lakes of Polessye). Melioracia i Vodnoje Khozyaistvo, N3, 8-12. Karkutsiev, G. I. (1982) Gidrologicheskie Aspekcyosushirelnych Melioratsii (The hydrological aspects of drainage amelioration activities). Kiev. Moklyak, V. I. (1973) Ob otsenke vliyania osushitelnych meropri-yatii na nekotorye kharakteristiki stoka malych rek Polessja i lesostepi Ukr. SSR (On the estimation of drainage effects on some characteristics of small rivers flows of Polessye and Ukrainian forest-steppes). Trudy GGI, N208, 168-172. Shabeko, V. B. (1983) Vliyanie Osushitelnych Melioratsii na Vodny Rezhimterritorii (The drainage amelioration effects on the water regime of some territories). Minsk. Sivko.T. N. (1956) GidrochimicheskieosobennostisrednegotecheniarekiPripyatipritokov(Thehydrochemicalproperties of the middle stream of River Pripyat and its tributaries). Trudy Kompleksnoi Ekspediciipo hucheniyu Vodoyomov Polessia, 56-68, Minsk. Vinberg,G. G. (1956)GidrobiologicheskyiocherkozeraChervonogo(ThehydrobiologicaldescriptionofChervonoyeLake). Trudy Kompleksnoi Expediciipo hucheniyu Vodoyomov Polessia, 3-18. Minsk.