Estimating the Volume of Stormwater Available for Harvesting in Urban Pima County

Pima County Regional Flood Control District Monthly Brown Bag Series

Speaker: Evan Canfield – Pima County Regional Flood Control District
Date / Time: Wednesday, January 10, 12–1PM
Location: 201 North Stone Ave, 9th Floor

Tucson has been in the midst of an extended drought, with 2017 being the hottest year ever recorded. The previous 3 years — 2014, 2015, and 2016 —were the next hottest on record. As a community, we have begun to study more seriously the use of rainfall and stormwater to supplement water supplies. Stormwater Harvesting and Management as a Supplemental Resource (2009), written by Pima County and the City of Tucson staff, supplemented observed rainfall and runoff data with a model that estimated runoff using daily rainfall data from 1895 to 2000. This evaluation suggested that about 30,000 to 40,000 acre-feet of water could be harvested from impervious surfaces in the City of Tucson in an average year. However, rainfall totals since 2000 have been on the decline.

This presentation will explain the data and modeling used to estimate stormwater volume from impervious surfaces in Tucson, and the effect that adding the last 17 years of climate data has on updating the estimate of harvestable stormwater. We will also discuss the potential of newly-derived land cover datasets to help us more-precisely estimate the extent of impervious surfaces, and the amount of stormwater generated from them.

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