Abstract
There are 17,076 stream miles listed for Category 5 nonpoint source (NPS) water quality impairment on Idaho's 303(d) list. Nearly 40% of NPS impairment in the U.S. is attributed to agricultural activities, with sediment comprising ~15% of this water quality pollution. Best management practices (BMPs) have developed to mitigate NPS pollution; however the need for site-specific research and an improved understanding of hydrologic processes persists in order to continue development and application of these practices. In the semiarid western U.S. water plays a defining role in public land use, with soil moisture, vegetation, and microtopography being key variables in the hydrologic function of ecosystems. Within the State of Idaho alone, 6 million hectares (~28%) of public lands are managed directly as grazing allotments, the majority of which are in semiarid areas. The most prominent microtopographic features in semiarid systems are `cat steps' or `terracettes', described as soil surface variations of <1 m consisting of repetitious `benches', path-like, and `riser', slope-like, features on hill sides of greater than ~15% slope. Due to limitations in the spatial resolution of topographic data and computational resource demands, hydrologic models have not accounted for terracettes despite a general recognition that influences of microtopography on soil moisture patterns in semiarid ecosystems can increase the accuracy of variables used in the modeling of processes such as surface runoff and sediment transport. The importance of sustainable rangeland management and the need to address water, erosion, and sedimentation challenges in semiarid ecosystems exemplifies the need to contextualize the hydrologic response of terracettes at a plot-scale and quantify their extent at a regional scale to inform sustainable BMPs and bridge water resource science, management, and policy.