CS(AR)-19/96-97 : Conjunctive use studies in Pennar delta, canal system : ground water balance for Southern channel command area

Abstract

Nowadays with the increase in demand of water for competing uses, it is not only difficult to meet the entire demand from a single source but also becoming challenging to plan and distribute different water resources for proper management. In a hydrological system surface water flows, low or high, do not necessarily coincide with the low or high levels in groundwater, because of the sluggishness of the groundwater flow compared to surface water flow. Also excessive development of groundwater in the deltas and coastal areas may lead to salt water ingress into the freshwater aquifer and may contaminate it, if unchecked. This may happen when sufficient surface water supplies do not reach the tail ends of command areas.

With the increasing knowledge of the hydrogeological features of potential aquifers being identified with latest geophysical investigations, the scope for better conjunctive use practices are very good. The prospects of practicing conjunctive use of surface and groundwater will be better provided one understands the hydroctimatology of the study area alongwith hydrogeology of the region. Though practicing of conjuctive use requires collaboration between different government authorities and non - governmental organisations, scientifically and technologically sound planning is also important. Understanding and monitoring the water balance of the system very closely will help in better conjuctive use practice. As a farmer switches over to using groundwater when there is frequent shortage of dependable surface water supplies the practice of conjunctive use is user friendly natural resort as far as practicing is considered. Hence cultivators will be accommodative to suggestions on conjunctive use provided maximum benefit is assured.

The pertinent data from village level of the Southern Channel Command area of Penner delta system in Nellore district of Andhra Pradesh is utilised and analysed to arrive at the groundwater balance of the system. In this report with a view to lake up conjunctive use practice in southern channel command area of Penner delta canal system, water balance components are estimated on seasonal basis for monsoon and non-monsoon seasons from 1989-1993. The crop water requirements are estimated for this period to find out the system demand. Various supply and use components are accounted for the study area using suitable techniques based on the availability of observed data. From the water balance equation rainfall recharge Eluting monsoon season is estimated to find out relationship between rainfall amount to recharge coefficient for the area