Abstract
This paper addresses applications of environmental isotope techniques in the study of some specific hydrological problems in the vicinity of Tarbela Lake and Chashma Barrage which are being recharged by the Indus River. The Indus River is one of the world's great rivers and the longest one in Pakistan. It originates from Tibet and after draining through the major length of Pakistan, falls into the Arabian Sea near Karachi. The major tributaries of the Indus River upstream Chashma include rivers: Kabul, Kalpani, Haro, Soan, Kurram and Tochi. The tributaries downstream Chashma include the rivers:Jhelum, Chenab, Ravi and Bcas/Sutlej.
The Indus River is not only a major source of recharge to the groundwater reservoirs along its course but it also provides water to the world's largest earth-filled dam namely 'Tarbcla Dam' for hydro-clectric power generation. At various barrages along its course such as Chashma Barrage, its water is regulated for canal irrigation. The variations in the concentrations of pollutants and the discharge of the Indus River depend upon those of its tributaries and the type of industrial and agricultural activities alongside. From a view point of groundwater resources development and environmental pollution, it is thus very important to determine the origin of subsurface water and its contaminants, recharge mechanisms, and interaction between aquifers recharged by the Indus River. The problem of growing waterlogging and associated salinity in the interfluvial areas of the Indus basin is also of great concern.
Although various water management agencies in Pakistan have done extensive studies on the hydrological problems of the Indus basin using classical techniques, the applications of environmental isotope techniques have yielded more accurate results regarding the ground water recharge mechanism, causes of waterlogging, the origin of salinity, and farm irrigation practice for remedial measures against waterlogging. The isotopic mapping of Indus River and the associated surface water and ground water reservoirs at various points along its course are discussed in the context of remedial measures.