Hydrological Processes and Modeling

sampling stream depth and quality

Hydrology and watershed analysis is the science of understanding how water moves through watersheds, and using that knowledge to preserve the world’s valuable water resources and use them efficiently, while also protecting communities from floods and other water hazards.

Water movement is highly variable in space and time, from small scales (e.g. water draining through soil cracks) to large scales (e.g. interactions of surface and groundwater focused within river margins). Faculty and students in the Geography Department often conduct fieldwork in the San Diego region and further afield, to collect hydrologic data such as river flow gauging, water quality analysis and isotope sampling. Watershed analysis uses extensive spatial information, often using remote sensing and GIS layers, such as data on land use, soil type, geology and human activities in the watershed.

Our research includes how to represent physical hydrologic processes in spatial, statistical, and computer models. We can use those models to predict hazards (floods, droughts), forecast water availability and test the results of future water management scenarios. We can predict the movement of pollutants and sediment through the watershed.


We collaborate extensively with local government authorities and nonprofits who work to manage and improve water resources in San Diego. These include City of San Diego, County of San Diego Watershed Protection Program, and San Diego River Park Foundation. Our Faculty are part of the SDSU Blue Gold Area of Excellence Leave geography site that coordinates water research across different departments; and the SDSU Watershed Science Institute Leave geography site.

SDSU Geography offers multiple courses in hydrology and water resources (listed below), and offers a Master’s degree in Watershed Science for those wanting to take their studies further. Our faculty supervise PhD students undertaking research in hydrology, through our Joint Doctoral Program with UC Santa Barbara.


students installing autosampler

Groundwater sources in San Diego’s Mission Valley

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, Hilary McMillan and Master’s student Sierra Wallace 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.

alyson scurlock at poster presentation

Urban Agriculture in San Diego: Environmental benefits and pressures

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. In this project, Hilary McMillan and Master’s student Alyson Scurlock 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 uses 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.

students meeting with water authority staff

Stormwater Re-Use in San Diego

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. Hilary McMillan and five Undergraduate 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.

panta rhei logo

Change in Hydrology and Society

From 2015-2017, Hilary McMillan was Chair of the International Association of Hydrological Sciences flagship project ‘Panta Rhei: Change in Hydrology and Society’. The project brings together more than 400 scientists from around the globe to understand and predict the interactions of society and water, to support sustainable water resource use under changing climatic and environmental conditions.

Water policy and management along the US-Mexico border

Trent Biggs leads multiple projects studying water policy and management along the US-Mexico border and in San Diego County, including impacts of changing water policy, irrigation efficiency measures and canal lining on groundwater recharge and groundwater availability.

student measuring sediments heights

Sediment loading into the Tijuana Estuary

Trent Biggs and Ph.D. Student Kris Taniguchi completed a project to determine the dominant controls on the sediment load from small, often unregulated urbanized watersheds in Mexico that drain to the Tijuana Estuary. Methods used in this project include use of 3D imaging of stream channels, using drones, Go-Pro video and manual surveying techniques.

measuring coral reef underwater

Land Based Pollution of Coral Reefs, American Samoa

Trent Biggs conducts research on sediment and nutrient loading to coral reefs in American Samoa, to quantify the impacts of pollution on the health of these reefs.



Scientific understanding of human-environment systems; sustainable management of natural resources under changing global conditions; role of science in addressing environmental issues and development of environmental and conversation policy.

Hydrological processes to include precipitation, surface water, groundwater, water quality, and ecohydrology. Impact of human activities on water resources.

Hydrologic processes and regimes, how these are affected by environmental change and how hydrologic process and regimes affect patterns of environmental change. Processes operating at global, regional, and local scales are examined, including land-use/ land-cover change and climate change.

Occurrence and utilization of water resources and the problems

Theory and techniques in watershed analysis. Use of GIS and statistical programming for analyses of geomorphology, hydrology, and water quality data.

Advanced special topics in geography. May be repeated with new content. See Class Schedule for specific content.

Spatial analytic techniques from image processing, remote sensing, geographic information systems, cartography or quantitative methods. May be repeated with new content. See Class Schedule for specific content.