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Catching Water in the Desert

An animation project about water harvesting in stream channels. How has the landscape in the dry grasslands of Arizona changed over time? How have humans affected the stream channels? In this region, most groundwater is recharged through the sediment at the bottom of stream channels. So how might changes in the channel affect the rates of infiltration (floodwater at the surface soaking into the ground) and recharge (the infiltrated water traveling down to the water table and being stored)? More information at the USGS Aridland Water Harvesting Study: https://geography.wr.usgs.gov/science... This video is based on background research for my MS Thesis: "The Effect of Gabion Construction on Infiltration in Ephemeral Streams" The full thesis can be accessed here: http://search.proquest.com/openview/9... The video is also available on the Arizona-Sonora Desert Museum site: http://www.desertmuseum.org/videos/sh... Subtitles available in French & English (Spanish coming soon). Abstract: Low-tech rock structures called gabions are commonly used in dryland stream channels to reduce erosion, slow floodwaters, and increase infiltration. Gabions may also increase water availability for riparian vegetation, and increase the duration of surface flow in ephemeral stream channels. However, their effects on infiltration and recharge are not well-understood. This study tested low-cost methods for easily quantifying the total infiltration induced by gabion construction in an ephemeral stream channel, over the course of a single flow event. We used well-established methods to find point infiltration fluxes from subsurface temperature time-series. Unique to this study, we then upscaled these measurements to the gabion’s entire area of influence using time-lapse photo data, which recorded the onset of flow and the duration of ponding. For a flow lasting ~5 hours, we ran 225 model scenarios, estimating that a single gabion could have increased the total infiltrated volume in the channel reach between it and the next gabion by as much as 255% or as little as 0%, but the most likely scenario is a 10.8% increase. We found the photo data to be invaluable in obtaining these estimates, and in understanding the dynamics of a remote field site. Future work would benefit from more precise measurements of point infiltration fluxes and better records of ponded surface area over time. If these improvements are made and our estimates can be replicated reliably, they would suggest that gabions are a more powerful restoration and management tool than previously understood.