Spatial and temporal assessment of groundwater behaviour in the Soan Basin of Pakistan

The assessment of groundwater potential for any region is very important for its sustainable management. However, the groundwater potential of the Soan basin - a sub basin of the Indus basin, has not been assessed after 1981, though large scale water resources development and exploitation activities have been carried out during the last two decades. A study was undertaken in the Soan basin to assess its spatial and temporal variability of groundwater potential and to propose measures for its sustainable management. Water-table data at 193 monitoring points were collected from 2003-2006. Long-term records 1960-2005 of rainfall at different stations, basin outflows and data on water resources development in the area were collected. There is a high spatial and temporal variation in rainfall over the basin. The rainfall pattern has changed over the basin, resulting in reduced basin outflow especially after 1984. After the drought of 1997-2000, the rainfall situation improved however, no significant increase in the basin outflows was observed. Since 1981, the groundwater utilization has increased significantly due to about 95% increase in the population. The number of open wells, hand pumps and tube wells has increased by 39, 186 and 96%, respectively over the last two decades. The increased abstractions of groundwater, reduced rainfall, and basin outflow have resulted in depletion of groundwater. The average water-table drop in the basin is 3.75 m over the last 25 years with an average drop rate of 0.15 m per year. However, in areas away from the river and recharging sources, the water-table drop is much higher, mainly due to more abstraction than recharge. In the areas, where water storage facilities such as small dams, mini dams and ponds were developed, a rise in water table has also been observed. On an average, the annual rainwater potential of the basin is 3.44 x 10(9) m3, whereas only 80 x 10(6) m3 (less than 3%) have been harnessed so far through construction of small dams, mini dams and ponds. Under the present water scarcity conditions, there is a need to initiate integrated water resources management programs with a site specific focus on rainwater harvesting. If no mitigation measures are undertaken, the groundwater depletion is expected to jeopardize the future agriculture and socio-economic development.