Photographs coming soon…
This is an exciting and challenging time in fresh water science and resource management. There are numerous important problems that remain unresolved, despite decades of intensive effort, and new problems are emerging because of increased fresh-water demand, shifting land use, and climate change. At the intersection of all of these topics and challenges are communities, ecosystems, food systems, and industries, as well as agencies (regulatory and non-regulatory), non-governmental organizations, and individuals trying to function and thrive. The UCSC Hydrogeology group has worked for decades to address technical method and data gaps, explore and understand fresh water hydrologic systems, build collaborative opportunities, and solve practical problems. Our research is “translational,” focused on bridging gaps between theoretical and foundational exploration and hypothesis testing and day-to-day applications of new methods and tools to solve vexing problems. We have also engaged, and in some cases provided leadership, in developing a new class of incentives that can help top engage people, bypass bottlenecks, and make natural-human systems work better for all involved. Here is a brief overview of some recent and past projects. Please see the Publications page for links to papers. Please also see The Recharge Initiative page for information on this focused effort to protect, enhance, and improve the availability and reliability of groundwater resources.
Groundwater recharge is an under-appreciated frontier in hydrology, the primary inflow to most aquifers, and the most important major hydrologic flow that can’t be measured remotely. The UCSC Hydrogeology group has been engaged for several decades in studies of groundwater recharge, particularly managed aquifer recharge (MAR), a set of tools and methods that can enhance groundwater storage, benefit aquatic systems, and improve or degrade groundwater quality.
We developed and introduced a novel tools and techniques for using heat as a tracer, through time-series analysis of subsurface temperature records to extract information on vertical seepage rates, both into and out of sediments underlying streams, rivers, ponds, infiltration basins, wetlands, and other systems. This approach allows relatively simple collection of useful data, based on naturally occurring variations in the temperature of surface water, and side-steps many challenges in coupled fluid-heat transport as has been commonly applied with numerical tools. Most importantly, the time-series method avoids problems with low-frequency (long timescale) variations associated with monthly, seasonal, annual, and decadal variations that have confounded more conventional approaches. Processing is rapid, allowing interpretation of annual records in a few minutes, and can provide essential information on both spatial and temporal dynamics of seepage, infiltration, and recharge..
We have advanced methods and conducted studies of regional suitability of sites for MAR, using a geographic information system and multi-criteria decision analysis. These studies link data on elevation and slope, land use, soil properties, shallow geology, hydrogeologic properties, historical groundwater levels, water quality, and other information to classify MAR potential. There is a global literature on use of MCDA for classifying MAR suitability, but little standardization of methods or testing of results to determine if they are correct or help to develop successful MAR projects. We are have also expanded this approach by linking regional groundwater models and simulations of stormwater runoff, leveraging hydrologic knowledge to improve planning and implementation of projects to enhance and sustain resources
We have helped to design and construct MAR systems that can use stormwater to replenish groundwater resources. As part of this work, we have explored methods for enhancing water quality, by stimulating ambient microbes to cycle nitrogen compounds, by adding bioavailable carbon to shallow soils. This work began with plot-scale studies, and has since been extended considerably to include more environments, paired laboratory core experiments, adding carbon to soils below operating MAR infiltration basins, and machine learning as applied to spatial data. We have collaborated with water and soil chemists and microbiologists to resolve where, when, and how denitrification can be enhanced during infiltration for MAR, even in coarse and low-carbon soils. We have also examined mobilization of geogenic metals in association with redox changes during infiltration, and the fate of metals once they are mobilized. We are putting these results to work by adding bioavailable carbon to MAR field sites, and we are actively monitoring and sampling these systems to verify performance in improving water quality.
We developed California’s first recharge net metering (ReNeM) program, in collaboration with the Resource Conservation District of Santa Cruz County, which compensates landowners and tenants for running projects on their properties that enhance infiltration and recharge in the Pajaro Valley. The concept combines elements of net energy metering and water banking, but is different from both in important ways, including: ReNeM incentivizes behavior that generates basin-wide benefits, rather than “saving” water for a single user; it is revenue positive for the participating agency; and it is based on making relatively simple measurements on the ground that are quantified by a “third party certifier” (TPC). The UCSC Hydrogeology group and the Resource Conservation District of Santa Cruz County (RCD) serve as the TPC for the program, which launched initially as a five-year pilot. The program has generated considerable benefit, despite periodic droughts, and the Board of Directors for PV Water subsequently removed the “pilot” designation. A cost-benefit analysis of ReNeM shows that it is cost-competitive compared to alternative options, while generating important co-benefits for people, communities, aquatic systems, and resource agencies. ReNeM and other components of our recharge research have generated considerable interest across the state and leveraged external funding that is supporting more extensive work. We are working on standing up the ReNeM program to operate going forward under RCD leadership, and seeding similar programs in other regions.