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 11 years including 2 years 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 < 0·0001) suggested that calibration predictions were highly significant and treatment prediction equations differ significantly. Results showed mean runoff reductions of 86·1, 60·5 and 37·7% 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 124·9, 77·1 and 40·0% for the W_T3, W_T2 and W_T1 over Wc, respectively. Paired t-test ( p < 0·001) 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 © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]