Urban agriculture is popular as a way to re-green our city landscapes and stem environmental degradation caused by industrial agriculture. However, local ecosystems and their capacity to support agriculture are highly variable, for example, urban agriculture competes for irrigation water in arid or semi-arid areas. This project will quantify and compare the environmental pressures generated by urban agriculture (e.g., water, fertilizer and pesticide use) and the environmental benefits (green space, soil productivity, biodiversity, and water conservation).
The project will use a variety of urban agriculture locations in San Diego, to investigate how location, garden mission, agricultural practices and socio-economic context, all change the ecosystem services and pressures of the urban agriculture site. Our aim is to understand how best practices can maximize the environmental benefits and productivity of urban agriculture.
Figure: MS student Alyson Scurlock presents her research into urban agriculture at the SDSU 2018 Student Research Symposium
Industrial associations in San Diego County must achieve compliance with the new Draft Industrial General Permit by capture and retention of 85% stormwater on their sites. Students are helping to identify the number of larger-scale industrial sites within the region that have the ability to store a large quantity of stormwater on site, identify how the water could be used and then quantify the amount of potentially stored stormwater.
This project is organized as a partnership with the San Diego County Water Authority, providing students with experience of professional hydrology careers.
Students meeting with San Diego County Water Authority staff to design the project scope and goals
Groundwater in the Mission Valley aquifer in San Diego is sourced both from rainfall on adjacent hillslopes, and from channel transmission losses. In this project for the City of San Diego, we are working to quantify the relative importance of those two sources. We aim to understand how and where different waters flow into and through the San Diego River watershed, and to differentiate between surface (river) and rain waters entering the Mission Valley aquifer.
We are using stable isotopes of water, including oxygen and deuterium, which can be used to identify sources of recharge to groundwater systems. Isotope “fingerprints” of rainwater, stream baseflow (low flow) and stormwater will be used to differentiate between these waters. Because isotopic composition of stream water can vary significantly during storm events, we are installing auto-samplers to take water samples at multiple time points during the storm hydrograph, to completely characterize the stormflow isotopic composition.
Figure: Pablo Bryant (Field Reserve Manager) and Sierra Wallace (MS Student) installing an autosampler location in a tributary of the San Diego River
From 2015-2017, I was Chair of the IAHS hydrological decade 2013-2022 with the theme `Panta Rhei: Change in Hydrology and Society’. The decade recognises the urgency of hydrological research to understand and predict the interactions of society and water, to support sustainable water resource use under changing climatic and environmental conditions.
I led the instrumentation of an experimental catchment in the Canterbury high country in the NZ South Island, to study catchment processes in upland environments. These upland environments are essential to provide water via streams and groundwater flows to the agricultural areas on the coastal plains downstream.
We installed a climate station, rain gauges, flow gauges, deep wells, tensiometers, sap flow sensors and nests of instruments including soil moisture sensors and shallow groundwater wells. Isotope sampling was used to track water sources for vegetation and streamflow.
Results of the study were published in HESS: “Characteristics and controls of variability in soil moisture and groundwater in a headwater catchment“.
I led a team of scientists at the National Institute of Water and Atmospheric Research (NIWA), NZ, to provide operational flood forecasts for rivers around New Zealand. Forecast users include local government emergency managers and hydro-electric power companies.
The project involved coupling Numerical Weather Prediction model forecasts to rainfall-runoff models to provide flood forecasts; including the use of Kalman filters for assimilation of discharge measurements to correct model states.
Ongoing work includes using ultra-high resolution weather forecasts and extension of the flood forecasting system to all catchments (gauged and ungauged) in New Zealand.
I designed a suite of hydrologic models with flexible structures that can track water, tracers and contaminants through catchment systems.
These models enable us to use tracer data as well as flow data to test hypotheses about how, where, and how fast water moves through a catchment. The flexibility of the model design enabled individual model components to be mixed and matched, to test each part independently.
The models were tested in catchments in Scotland where sea salt provides a natural tracer. Our results showed that using tracers can help us choose the best hydrologic model structure, where flow data alone cannot distinguish between the models. The results provided insight into the extensive mixing of water in soil and groundwaters that occurs even within small catchments.