Abstract
Concerns over freshwater scarcity for agriculture, ecosystems, and human consumption are driving the construction of infiltration trenches in many mountain protected areas. This study examines the effectiveness of infiltration trenches in a subalpine forested catchment in central Mexico, where public and private organizations have been constructing trenches for ~60 years. We rely on empirical data to develop rainfall-runoff models for two scenarios: a baseline (no trenches) and a trenched scenario. Field measurements of infiltration capacities in forested and trenched soils (n = 56) and two years of meteorological data are integrated into a semi-distributed runoff model of 28 trenched sub-catchments. Sensitivity analysis and hydrographs are used to evaluate differences in total runoff and infiltration between the two scenarios. Multiple logistic regression is used to evaluate the effects of environmental and management variables on the likelihood of runoff response and trench overtopping. The findings show that soil infiltration capacity and rainfall intensity are primary drivers of runoff and trench overtopping. However, trenches provided only a 1.2% increase in total infiltration over the two-year period. This marginal benefit is discussed in relation to the potential adverse environmental impacts of trench construction. Overall, our study finds that as a means of runoff harvesting in these forested catchments, trenches provide negligible infiltration benefits. As a result, this study cautions against further construction of infiltration trenches in forested catchments without careful ex ante assessment of rainfall-runoff relationships. The results of this study have important implications for forest water management in Mexico and elsewhere, where similar earthworks are employed to enhance runoff harvesting and surface water infiltration.
Highlights
A wide variety of approaches to water resource management have been implemented in mountain protected areas [1]
All time to concentration values were below 6.6 min, meaning that runoff travel time in each catchment to the downslope catchment or to the downslope trench took less than 6.6 min (Appendix A Table A1)
This study examined the effectiveness of infiltration trenches in a subalpine forested catchment in Mexico
Summary
A wide variety of approaches to water resource management have been implemented in mountain protected areas [1]. Increased groundcover is generally associated with enhanced water retention and quality, infiltration, and groundwater recharge, though the direction and strength of the effects depend critically on relationships between soils, vegetation type, and climatic factors [9,10]. Such nature-based solutions have proven highly effective at mitigating the impacts of runoff in forests [11] and on agricultural lands [12]. The use of ‘natural’ vegetation, whether as hedgerows [13], grass strips [14], other herbaceous cover [15], and trees generally provide more sustainable and cost-effective strategies for surface water management [16,17]
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