A simple method using farmers' measurements applied to estimate check dam recharge in Rajasthan, India

Since the 1960s more than 200,000 check dams have been constructed on ephemeral streams in India to enhance groundwater recharge and help sustain irrigation supplies. While many farmers, non-government- and government organizations attest to check dam effectiveness, very few (<30) have been quantitatively evaluated and results have been variable. The paper describes the application of a simple daily water balance calculation to four check dams near Udaipur in southern Rajasthan where farmers took daily measurements of check dam water levels and rainfall for 2 years. The farmer measurements were proven to be highly reliable. They revealed that the check dams augmented recharge by 33 mm in 2014, an average year, and by 17 mm in 2015, a dry year (where recharge is expressed as depth over the combined catchment area of the check dams). This corresponded to 2.0 and 1.0 times the combined capacity of these check dams in those years, and the average annual recharge volume, 743,000 m(3), supports 16% of agricultural production in the rabi (winter) season from the surrounding villages. Total recharge was estimated to be 37% and 70% of combined runoff in 2014 and 2015, respectively. Mean dry weather infiltration rates averaged from the four sites over both years were 5-8 times the evaporation rate from check dams. Hence, based on farmer measurements, it is conclusive that the studied check dams are effective and efficient in recharging the local aquifer. The paper demonstrates that a simple method can be used by farmers with basic training to determine the need for desilting of check dams in the following dry season and to provide essential data to allow quantification of recharge from check dams. This opens the possibility of scaling up by orders of magnitude the number of check dams evaluated. With more check dams monitored over longer periods, quantitative data would become available to inform on sizing and placement of check dams in relation to local benefits, capital and maintenance costs and downstream impacts, and thereby to inform future investment in check dams.