PINSTECH/RIAD-122 . SURFACE WATER/GROUNDWATER RELATIONSHIP IN CHAJ DOAB RADIATION & ISOTOPE APPLICATIONS DIVISION Pakistan Institute of Nuclear Science & Technology P. O. Nilore Islamabad. JULY, 1990 PINSTECH/RIAD-122 SURFACE WATER/GROUNDWATER RELATIONSHIP , IN CHAJ DOAB S. D. HUSSAIN M. I. SAJJAD W.AKRAM M. AHMAD M. RAFIQ J. A. TARIQ RADIATION & ISOTOPE APPLICATIONS DIVISION Pakistan Institate of Nuclear Science & Technology P. O. Nilore Islamabad. JULY, 1990 PIMSTKCH/RIAD-122 SURFACE WATER/GROUNDWATER RELATIONSHIP IN CHAJ DOAB S.D.HOSSAIN M.I.SAJJAD W.AKRAM M.AHMAD M.RAFIQ J.A.TARIQ RADIATION & ISOTOPE APPLICATIONS DIVISION PAKISTAN INSTITOTE OF NUCLEAR SCIENCE & TECHNOLOGY P.O. NILORE, ISLAMABAD JULY-1990 CONTENTS ABSTRACT INTRODUCTION 1 DESCRIPTION OF THE AREA UNDER INVESTIGATION 2 2.1 General 2 2.2 Physiography 2 2.3 Geology 3 2.4 Climate 4 SAMPLING PLAN 5 ANALYSIS 6 ISOTOPIC CHARACTERISATION OF DIFFERENT HATERS 8 5.1 Rainfall 8 5.2 Surface Hater: Rivers and Canals 9 5.3 Groundwater 11 INTERRELATION OF DIFFERENT WATERS 12 6.1 Surface Water/Shallow Groundwater 12 6.2 Shallow Water/Deep Water 14 6.3 Surface Water/Deep Water 15 PROCESS OF SALINIZATION OF GROUNDWATER 16 CONCLUSIONS 17 ACKNOWLEDGEMENTREFERENCES S 1189 ABSTRACT In order to understand the relationship between surface water and groundwater in Chaj Doab, isotopic and chenical studies were undertaken. The data show that north-eantern part of the doab is mainly recharged by raini;. In the rest o* the doab, surface water and groundwater are generally well connected and the recharge is mostly from the rivers either directly or through irrigation channels. Salinization of groundwater is mainly due to dissolution of salts from the r.oil sediments. 1. INTRODUCTION Pakistan is located on a great land Bass north of the tropic of cancer between the latitudes of 24* and 37°N and longitudes of 61"and 75*B. Landscape varies from flat alluvial plain to mountainous / subBountainous territories. The cliaate is generally tropical /subtropical. SuBBer temperature reaches 50 C at some places while Biniaua winter temperatures are several degrees below freezing point at sose other places. Precipitation is scanty, average annual rainfall in the Indus Basin is less than 375 BB whereas subaountainous tracts in the north and north-east of the Indus Basin receive 750-1000 BB rainfall annually . In general, Pakistan is seai-arid/arid. Evaporation is high due to the prevailing high teaperatures and low humidity. Precipitation-wise, Pakistan is water-deficient. Agriculture plays an important role in the economic growth of Pakistan. This, in turn, depends on the intricate canal irrigation system which has been in operation mostly in some parts of the Indus Plains for over a hundred years. Seepage from the unlined irrigation channels has raised the water table considerably resulting in the waterlogging and salinity problems In order to understand the relationship between surface water and groundwater in the interfluvial area between the rivers Jhelum and Chenab (Chaj Ooab), isotopic and hydrochemical methods were applied. The environmental isotopes like Deuterium ( H or D ), Oxygen-18 ( iB0 ), Carbon-13 ( 19C), Tritium ( 9H or T ) and Carbon-14 ( C ) alongwith common chemical ionic concentrations have been measured in water samples collected froa different places. The description of the area under investigation, the work carried out and the results obtained are as follows: 1 2. DESCRIPTIOH OF THE AREA UHDKR INVESTIGATES 2.1 General The interfluvial tract of land between the rivers Chenab and Jhelun is known as Chaj Doab and is shown in figure 1. It is a part of the Indus Basin and covers an area of about 1.4 million hectares including about 0.2 Billion hectares of piednont plain. The average elevation of the doab is about 203B above Bean sea level' . The gradient in the piedmont plain is ca. 2.3 meter/kn and ranges in the rest of the doab from about 60 cn/km in the north-east to 20 ca/ka in the south-west near the confluence of the rivers Chenab and Jhelum. Two major unlined canals viz. Lower Jhelum Canal (LJC) and Upper Jhelum Canal (UJC) have been in use for irrigation purposes since 1901 and 1915 A.D. respectively. There has been an appreciable rise in water table in the area . Large tracts of irrigated land have been adversely affected by salinity and waterlogging. The reclamation of the soil does not keep abreast with the rate of deterioration with the result that productivity of agricultural lands is adversely affected. 2.2 Physiography In the northern part of Chaj Doab, Pabbi Hills, a part of Himalayan Foothills, rise 120-150 a above the surrounding area. The outcrops of the bedrock exposed in the south-western part of the doab are called Kirana Hills and rise to about 305 a above the surrounding land. The transitional area between Pabbi Hills and alluvial plain is known as piedmont area and ranges in width from 5 to 24 ka with gradients varying from 2 to 9.5 a/km. Heander belt and present flood plains of the rivers Jhelum and Chenab are as 2 •uch wide as 8 km and are known as active flood plain (figure 2). The area located parallel to the rivers, about 32 kn wide and a few meter higher than the active flood plain is called the abandoned flood plain. The central part of the doab rises abruptly 1.5 to 8 n high above the abandoned flood plain and is known as bar upland 2.3 Geology The dominant geologic unit in Chaj Doab is alluvium. The exploratory drilling carried out by Water and Power Development Authority (WAPDA) showed that the alluvium of Quaternary age has been deposited on semi-consolidated Tertiary rocks or on a basement of metamorphic and igneous rocks of Pre-Cambrian era The alluvium consists of uncosolidated fine to medium-grained sand and silt and minor amounts of gravel and clay. The alluvium is heterogeneous in character and individual strata have little lateral and vertical continuity. The sediments constituting the alluvium have been transported and deposited by the present and ancestral tributaries of the river Indus. The distribution of the Tertiary rocks is known only in the north-eastern Chaj Doab in Pabbi Hills area where rocks of Siwalik system are exposed. Three of the geologic units are of subordinate regional significance: the Potwar loess, piedmont deposits, and aeolian deposits. The occurrence of the Potwar Loess is restricted to the northern flank of the Pabbi Hills. The Piedmont deposits are confined to a narrow belt, generally less than 24 km wide adjacent to the Himalayan Foothills and the Salt Range. The piedmont deposits consist of poorly sorted sand and gravel near the hills, grading into clayey sand and silt. The aeolian deposits are found in small local 3 areas in the lower reaches of the project area. However, their separation from alluvium is impracticable The bedrock hills at Rirana represent the peaks of a burrieu rirtge which underlies the central part of Chaj Doab. The north-eastern flank of the ridge dips steeply beneath the alluvium and only a few kilometers away from the outcrops the alluvial material has a thickness of more than < 7 > 457 m . The blocking or damming effects of the bedrock outcrops on the regional movement of groundwater are negligible because of the large gaps between bedrock outcrops and the occurrence of sandy zones intercalated everywhere in the alluvium 2.4 Climate The climate of Chaj Doab is sub-tropical continental influenced by large fluctuations in temperature and rainfall. It ranges from semi-humid in the north-east to semi-arid in the south-west with hot summers and cool winters. Average temperature during June/July is 34 °C while that in December/January is 12 °C As the doab is located on the fringe of the monsoon belt, the monsoon rains mostly occur from mid July to mid September. The rains come from moisture laden winds arising from the Bay of Bengal. The winter rains are the result of movement of cyclonic winds which originate from the Mediterranean Sea. It has also been observed that on most occasions western disturbances play an im* ~>rtant role in the production of heavy spells of rainfall during June to October . The average annual rainfall ranges from about 1000 mm in the north-east to about 230 mm in the south-west. About 65 to 70 % of the rainfall occurs during the monsoon 4 period 3. SAMPLING PLAN Chaj Doab xs irrigated fron the canal system derived from the river Jhelum. Hotor-driven pumps/tube-wells supply ground water for irrigation purposes. The wells penetrate to depths of about 150 m. Hand pumps are generally installed to tap shallow water for domestic use. The depth of hand pumps ranges from 6 to 15 m in the plain area while that in the northern part of the doab ranges from 8 to 24 meters. The sampling stations are spread over the entire area under investigation as shown in figure 3. Seven sets of samples were collected during the period November 1985 to October 1988. First five sets of water samples were collected from 46 hand pumps and 37 tube wells. After the examination of preliminary isotopic results, more sampling stations were added in the areas needing more consideration and the number of sampling stations became 86 and 49 for shallow and deep water respectively. Bain samples were collected from station number 33 with the collaboration of Meteorological Department. Sampling of stagnant water was avoided. Temperature, pH and electrical conductivity (KC) measurements were made in situ. Samples were also collected for C analysis from different stations where tritium content was found less s than 5 TO * after examining the preliminary isotopic results.