Ground Water Depletion on Kathmandu Valley
Water is an essential component for every life on earth. Without water, life seems impossible. Despite this fact, there are various parts of the world which lack the life-saving water. Kathmandu valley is a good example of the place with chronic water shortage. The daily demand for water in the Kathmandu valley is estimated to be more than 320 million liters. Unfortunately, one percent of the water demand is hardly fill in Kathmandu valley.
To cope with water scarcity problem Nepal government proposed a project of inter-basin transfer of water from Melamchi River located 40 km northeast of the Kathmandu valley. This water diversion project is estimated to bring 510 million liters per day by 2025. But this does not seem to be the reliable solution due to huge growth rate 4.7% in Kathmandu valley. The Melamchi river diversion project was established in the year 1998 with the objective of supplying water from the Melamchi river to the Kathmandu valley. But at the end of 2012 only around 11 percent of work is almost complete.
Out of 313 stone sprouts, only 59 are running and the rest is dried. It is mainly due to unsustainable withdrawal. Due to scanty available of another source of drinking water pressure on ground water seems to rise steadily. As Groundwater depletion is a great problem in Kathmandu valley. Ground water depletion scientifically is the decrease of the water table. The zone above the saturated zone is the water table. Below the water table, there is water and above it does not hold water. Ground water depletion is caused by withdrawing of ground water more than it is recharge naturally.
Naturally, water gets recharged by the rain water, flowing streams and ground water movement. Rainwater in natural condition gets abstracted by vegetation and the water infiltrate inward thus helps to recharge. Ground water movement can contribute scantly on recharge because its movement is too slow around thirteen centimeters per day.
Depletion of ground water can be best understood by using credit card example. The credit card gives money up to a certain limit even though we don’t have any deposited money on our account. The same is true for water. Land can give water up to a certain point without adverse effect. There has been the concern in the Kathmandu valley in recent thirteen years that ground water is getting depleted year after year.
Thirty years before one can get the water by digging eight meters below the ground level. But, now one can hardly get water by digging more than thirty meters. It is estimated that the groundwater is depleting at one meter per year. The total sustainable withdrawal of groundwater from the valley's aquifers is approximately 26.3 million liter per day, but the total currently extracted is about 58.6 million liter per day.
The possible consequence of groundwater depletion can be sobering. More energy will be needed to pump water out of ground water, which ultimately increases the cost of operating the water pump. The most devastating effect can be on the land subduction. Due to void space in beneath, there can be subduction of the ground anytime. This might have devastating effects. It may cause huge property damage and casualties. So, immediate action needs to be done on this particular task.
Preventive measures can be withdrawn water at a sustainable rate and increasing the place of recharge for an aquifer. There should be awareness of withdrawing water and sustainable rate and increasing the vegetation cover with decreasing the run off of water and increase the infiltration rate. Nowadays there are multiple options made available for ground water recharge.