Assessment of groundwater potential and threats for its sustainable use, case study of greater Thal Canal area from Punjab Pakistan

Introduction: The Indus River Basin is one the largest basins in the world having an area of ۱.۱۷ million Km۲ which supplies water to a large contiguous irrigation system for about ۹۰% of the food production in Pakistan. Due to rapid growth of population, agricultural intensification, climatic variability, industrialization, urbanization and lack of holistic regulation for groundwater development and use, the aquifer underlying the Indus Basin is under stress. This well transmissive and extensive alluvium aquifer covers an area of ۱۶.۲ Mha in Pakistan and is contributing about ۴۰-۵۰% towards the irrigation water requirements in addition to domestic, industrial and other commercial demands. Materials and Methods: A study to evaluate the current potential and threats for groundwater has been carried out in Thal Doab which is partially arid and desert area and is the part of large Indus River Basin. Recently, the irrigation is being extended through construction of four new canal-systems under Greater Thal Canal (GTC) project being funded by the Asian Development Bank. At present, farmers are pumping groundwater by installation of tubewells generally run by electricity and diesel as energy source; however, trend of solar tubewells is also on the track. Results have revealed that depth to water table in GTC area and its surrounding area is generally less -ranging from ۱.۵ m to ۶ m below the land surface- in the northern part and comparatively more - ۹ m to ۱۵ m- in the southern and eastern parts of the Doab. Results: Groundwater quality in the area is fresh, marginal to saline. Shallow groundwater quality (EC value) ranges from around ۳۰۰ to ۳,۷۰۰ uS/cm while for deeper groundwater it ranges from around ۶۰۰ to ۸,۰۰۰ uS/cm. In the central parts of the Doab, groundwater quality is generally poor. It has been observed that the direction of groundwater flow is from North-West to South-East and major source of aquifer recharge is the Chashma-Jhelum Link Canal. Construction of GTC systems and introduction of solar tubewells will change the hydrodynamics of the aquifer and for proper development, management and to keep balance between recharge and discharge components, an appropriate aquifer mapping, regular groundwater monitoring and modeling is required in Greater Thal Canal command area. For this, a proposal has already been submitted to ADB. Recently the Punjab Government has launched the Punjab Water Policy ۲۰۱۸ and the Punjab Water Act ۲۰۱۹ which govern the groundwater regulation. The present paper encompasses the expected consequences of all these interventions. Conclusions: Groundwater quality is also an important factor for its domestic and agriculture use. Fresh, marginal, and saline groundwater was observed in the study area. The ranges of groundwater (i) water with an EC reading of less than ۱,۵۰۰ uS/cm is considered as fresh, and (ii) water with an EC reading of ۱,۵۰۰ to ۳,۰۰۰ uS/cm is considered marginal as an irrigation water source, and (iii) water with an EC reading of greater than ۳,۰۰۰ uS/cm is considered as saline. Distribution of the shallow and deep groundwater quality in the GTC area is based on the monitoring of water from hand pumps, the piezometers and farmer’s tube wells installed in the area. In the Nurpur Tehsil area, Groundwater quality ranges from fresh to saline with the EC values from ۱۰۰۰ µs/cm to around ۷,۰۰۰ µs/cm.

کلیدواژه ها:

Groundwater ، Indus-Basin ، Thal Doab ، Greater-Thal-Canal ، Punjab ، Pakistan ، Irrigation system