Water quality and quantity responses to lawn irrigation and low-impact development in a semi-arid urban watershed.
Urban development in semi-arid grasslands can substantially alter streamflow regime and water quality, yet the timing and mechanisms driving these changes remain poorly documented. This study examines the water quantity and quality impacts of low-impact residential development in the West Stroh Gulch watershed in Parker, Colorado.Ìý
This watershed has been studied by the Hydro-Urban Bhaskar (HUB) group since 2020, spanning the pre-development to the development stage. Previous work focused on pre-development streamflow and sediment mobilization response to storms. In fall 2025, field monitoring revealed the emergence of baseflow in the historically ephemeral West Stroh Gulch, as a response to irrigation of non-functional turf medians adjacent to roadways upstream. This study tracks this ephemeral to perennial stream transition as it happens in the current early-development stage.Ìý
Radar-rainfall data is collected and combined with trail camera time-lapse photography data to identify periods of stream storm response, allowing us to isolate periods of base irrigation return flow. Installation of an H-flume system at the outlet of the watershed will provide stream flow rate readings during baseflow events. Water sample collection at the same outlet, analyzed for nitrogen and phosphorus concentrations, will characterize nutrient loads relative to storm-driven flows in nearby undeveloped watersheds.Ìý
Results are expected to show changes in streamflow frequency, duration, magnitude, and measure nutrient export associated with irrigation return flow. These findings provide novel field-based evidence of perennialization as a result of excess irrigation in a Front Range semi-arid urban watershed. Our results offer actionable insight for stormwater and water quality management in rapidly developing regions facing both wildfire and water scarcity pressures.