Tiny difference that made a miracle
The economic and ecological miracle of regeneration in Alwar district is being brought about by using just three per cent of the rainfall. This small percentage is being used for irrigation, and has made a tremendous change. The region is today thriving and prosperous. R N Athavale, emeritus scientist at the National Geophysical Research Institute in Hyderabad, visited some areas in Alwar where the Tarun Bharat Sangh (TBS) has worked. His aim was to assess the changes brought about by the water harvesting structures through certain estimates of the water balance of a typical river in the area. Athavale's findings are based on his experience and not on actual experiments or data collection in the area visited. But they provide an interesting insight into the dynamics of the new water management in the area. Here are some of his findings:
- The annual average rainfall in the region is about 600 millimetre. Most of this rain (about 80 per cent) falls during the monsoon. Before TBS's intervention in encouraging water harvesting structures, 35 per cent of the rainwater was lost immediately as seasonal run-off. Another 50 per cent was lost due to evaporation or transpiration (loss of moisture which evaporates from the surface of plants). Only 15 per cent of the rainfall naturally recharged the groundwater. Of this, 5 per cent became soil moisture, as the soil was too dry. Another 5 per cent constituted the base flow, implying the amount of groundwater returned to the surface stream or river. Of the remaining 5 per cent, some parts were tapped by wells and used, but the rest percolated to depths below the wells and stream beds.
- After water harvesting structures were built, there was an additional recharge of groundwater to the tune of 20 per cent.
- Though the base flow to the stream or river remained the same, there was an additional seepage (effluent seepage) of 17 per cent of rainfall to the river in non-monsoon months. This phenomenon contributed to the revival of the river and made it perennial.
- Seasonal run-off has come down from 35 per cent of the rainwater to only 10 per cent.
- There has been an increase in soil moisture: an additional 5 per cent of the rainwater is retained in the soil.
- Groundwater table has risen. In all 5 per cent of the total rainwater is being used for irrigation, one-third of which is returned to the ground. It should be noted that the villagers have not been unscrupulous in drawing out groundwater, which is quite common in areas where the government takes a flat rate for use of groundwater. A flat rate does not give any incentive to regulate the withdrawal of groundwater.
- It is not just that there is more water available for agriculture. Quite crucially, it is now available at critical stages of plant growth, which contributes to better yields. Before water harvesting structures were revived, water was not available at these critical stages, resulting in poor yields or crop failure.
- About 22 per cent of the run-off (excluding the 10 per cent seasonal run-off during the monsoon) is better regulated and spread out over the year. This has been crucial in reviving the Arvari. If this run-off had not been regulated, the river would not flow throughout the year. Which goes to show how fragile the ecosystem is.