Rainwater Harvesting Infiltration Exploration Using Hydrus-1D

Abstract

Rainwater harvesting is an emerging facet in the water supply portfolio for developing more drought-resistant cities in the arid-southwest, and bioswales are touted by some as a potential method to recharge aquifers. This research explores this claim through the use of Hydrus-1D. The objectives of this study were to test these claims by (1) examining how the choice of boundary conditions in a 1D soil-water model can result in different water content profiles, (2) exploring how soil, precipitation, and ponding conditions contribute to different depths of infiltration at bioswales within different time-frames, and (3) evaluating the efficacy of bioswales as a tool for recharge in the City of Tucson. The best boundary conditions found were time-variable boundary conditions to link atmospheric conditions to subsurface conditions. Three soils were selected to be representative of the soils found in the Tucson area: Loamy Sand, Loam, and Silty Clay. These three soils were put through various model time-frames and atmospheric conditions including monsoon season and multi-decadal stages with different influences. The influences explored were normal atmospheric conditions, higher precipitation to simulate runoff, root water uptake in the form of non-turf grass applied at the surface, and combinations of the above. For recharge purposes, Loamy Sand was the most effective soil for infiltration and recharge purposes through the variety of influences listed above. The models developed here, however, are limited in their representativeness of real-world conditions, and may provide initial guidance for future field studies and subsequent modeling.