Quantification of Hydrologic Response of Staggered Contour Trenching for Horti-pastoral Land Use System in Small Ravine Watersheds: A Paired Watershed Approach

A paired watershed approach was used to quantifying the effects of staggered contour trenching (SCT) densities on runoff and soil loss from a long-term field experiment. Four adjacent physiographical similar ravine watersheds were selected. After 2-year calibration period, three of the four watersheds were treated with different SCT densities and leaving one watershed as untreated control (W-C). The SCT densities of 139, 278 and 417 trenches ha(-1) were determined based on the targeted 25, 50 and 75% runoff trapping potential of the W-T1, W-T2 and W-T3 treatment watersheds, respectively. Runoff and soil loss were recorded for a period of 11years including 2years of calibration period. The calibration and treatment prediction equations for the treatment watershed with respect to untreated control watershed were developed by the simple linear regression. F-test and t-test (p<00001) suggested that calibration predictions were highly significant and treatment prediction equations differ significantly. Results showed mean runoff reductions of 861, 605 and 377% in the W-T3, W-T2 and W-T1 treatment watershed over the control, respectively. Similar trends as the runoff were also recorded in soil loss reduction by 1249, 771 and 400% for the W-T3, W-T2 and W-T1 over Wc, respectively. Paired t-test (p<0001) indicated that the means of the treatment effects on runoff and soil loss in treatment watersheds differ significantly with control watershed. It was concluded that 417 staggered contour trenches ha(-1) is an optimum trenching density for supporting the horti-pastoral land use system in ravine lands of India. Copyright (c) 2016 John Wiley & Sons, Ltd.