Monsoon-Rain Flow in an Ephemeral Channel near Sierra Vista, Arizona

As part of the assessment of the binational San Pedro aquifer, the effects of urbanization on runoff in ephemeral streams was studied. Ephemeral streams are those that flow in response to precipitation. Runoff in tributaries to the San Pedro River is important in understanding the water budget of the river. In addition, in arid watersheds such as the San Pedro, flow in ephemeral channels is potentially one of the most significant ways in which aquifers are recharged. To track runoff, we installed a network of 11 streamgages in ephemeral stream channels in and near Sierra Vista and Ft Huachuca, Arizona. The largest flow measured totaled nearly 70 acre-feet which is greater than the water contained in 1,000 14 ft x 34 ft backyard swimming pools, and we found that greater runoff occurred in the more urbanized stream.