Groundwater is a highly useful and often abundant resource. However, over-use, or overdraft, causes major problems to end users and to the environment. The most evident problem is a lowering of the water table. Wells must consequently be deepened to reach the groundwater.
Starting from the North and moving Southwards, the State can be divided into Five hydro-geological zones, the (1) Bhabar (2) Tarai (3) Central Ganga plains (4) Marginal alluvial plains and (5) Southern Peninsular zone. The water level is deep in Bhabar where as in Tarai auto flow conditions are noticed with piezometric heads of 6-9 magl. Low relief and numerous alluvial features characterize the Central Ganga plain. There are four major aquifers in the depth range of 700 mbgl. The yield of these tube wells ranges from 90 to 200 m3/hr. The thickness of sediments in Marginal alluvium is 50-300 m and yield of tube wells is between 35 to 70 m3/hr. The yield prospects of Vindhyan & crystalline rocks in the southern peninsular region are limited.
In U.P. ground water extraction exceeds recharge in over 100 development blocks and most of the large cities and towns. Urban water is in short supply. The problem of waste water generated from cities is growing.
In the rural and urban areas of the state, there are 10563 hydrograph stations which can measure the ground water level (pre & post monsoon only six times in a year. The difference in the water level in different areas of the state ranges from 2m.to 30m. and more. The major difference can be seen in the central and eastern region of U.P. The water is below 2m. in the Sharda Sahayak Canal Command areas whereas in the areas near the Ganges natural dykes it is found to be 20m. deep. The water level in the areas of the river basin of Yamuna & Betwa is found to be 40m. deep approximately. The main reason for this downfall is excess of water extraction from the ground for different and various reasons.
As per GEC-97 norms, groundwater potential was assessed on the basis of 01.04.2004 data by UP Directorate of Groundwater. This assessment showed that “the present groundwater potential/ availability in the State is 7.01 million ha.m, of which 4.88 million ha.m of groundwater is being utilized in a year”. In other words, 69% of groundwater resources had already been developed in UP by 2004. This percentage would have gone up since then.