In–situ rainwater harvesting through different intensities of staggered contour trenches in lower Himalayan region

Abstract

To evaluate efficiency of in–situ rainwater harvesting, three closely located micro watersheds were selected at research farm area of ICAR–Indian Institute of Soil and Water Conservation (ICAR–IISWC), Research Centre, Chandigarh. Land use of these watersheds is sparse mixed deciduous forest. Areas of micro–watersheds varied from 750 to 1225 sq m. Slope of micro–watersheds varied from 35.8% to 52.5%. Three treatments with 30%, 50%, and 80% retention of runoff from design storm were attempted in order to determine number of staggered contour trenches (SCTs) in each micro–watershed. The objective was to identify the design storm and intensity of contour trenches for resource conservation in the forest area. Runoff from micro– watersheds is gauged through 0.3 m deep 90o sharp crested weirs supported with water stage recorders. Runoff and sediment yield were recorded during monsoon season of 2015 to 2018 from all the three micro–watersheds. Year wise runoff analysis indicates that runoff varied from 8.3% (in 80% trenching) to 16.8% (in 30% trenching) of rainfall in the micro–watersheds resulting storage / conservation of 83.2% to 91.7% runoff. Similar was the trend of sediment yield. Average soil loss varied from 165.4 kg ha–1 to 967 kg ha–1, being highest in 2015 and decreased thereafter. Soil moisture was observed to be highest at the downstream of the micro watershed having trenching intensity of 80%. Study indicated that contour trenches with high intensity can harvest more runoff water and reduce runoff from watershed.