Research in the HSGG covers a broad range and can be organized into seven topical areas, although these are not formalized in the Group.  The areas with the largest number of faculty (in decreasing order) are Earth surface water patterns and processes, “critical zone” water, and hydrogeochemistry.  The other four areas (all led by at least three faculty members) are hydrogeology, physical hydrology, water resources management, and land-atmosphere interactions.  Faculty with primary emphasis in one area frequently are involved in other research areas, so this subdivision is flexible.

Earth surface water patterns and processes is a broad domain addressed by nine faculty members who investigate the details of surficial water storage and flux, including the interactions with landforms and biota.  Although faculty address fundamental physical mechanisms, there is substantial expertise associated with specific water-bearing landforms, including lakes, wetlands, rivers, estuaries, and even the ocean.  Faculty also work across spatial scales from turbulence at a point to watersheds and larger regions.  Heavily cited journal publication topics during the review period include use of imaging spectroscopy to study ecosystem processes and properties, locating sources of surf zone pollution, river rehabilitation design, effect of lake warming on planktonic diatoms, and advancements in numerical hydraulic simulation.  One of the first textbooks on the emerging discipline of ecohydraulics was published by an HSGG faculty member recently.

The “critical zone” is a relatively new term coined by the National Science Foundation to address the vertical gradient from the top of vegetation down to the base of weathered bedrock.  HSGG has six faculty members with their primary research emphasis addressing the critical zone.  Activities in this region span agricultural and environmental sciences, which makes this topic a long-standing core strength of HSGG and UC Davis as a whole.  Several faculty in HSGG are involved in the NSF Critical Zone Observatory program, with emphasis on the Southern Sierra Observatory that is directed by HSGG member Roger Bales.  The emergence of this facility in the region has promoted the application of traditionally agricultural-oriented research topics into the environmental sphere in the Observatory.  Heavily cited journal publication topics during the review period include regional sustainability of irrigated agriculture, hydraulics of plant growth, sensitivity of olive oil production to amount of water applied, carbon and nitrogen dynamics in forest and agricultural soils, and pesticide runoff from orchards.

Hydrogeochemsitry is a broad domain addressing chemical reactions, transport, and mass flux.  Although many faculty work on chemical transport, there are five faculty with primary emphasis on hydrogeochemistry as a whole.  Heavily cited journal publication topics during the review period include land use and land cover effects on water quality, biogeochemistry of dissolve and particulate organic matter in rivers, water-exchange rates on aqueous polynuclear clusters and at oxide-water interfaces, Stable hydrogen and oxygen isotope ratios of bottled waters of the world, and effect of climate change on winter chill for fruit and nut trees.

Hydrogeology here is meant to encompass all research into subsurface patterns and processes, including contaminant transport and bioremediation.  During the review period a highly prominent research program addressed the environmental effects of dairy wastewater.  Other highly cited research topics included river-aquifer interactions in light of geologic heterogeneity, occurrence and fate of pharmaceutically active compounds in the environment, and causes of natural attenuation of organic pollutants in groundwater.

Physical hydrology addresses investigation into the mechanisms of water storage and flux in an integrated way across the landscape, usually at watershed and regional scales.  A lot of research has been done to understand mountain hydrology, led by the faculty in this group, but also including others.  Also, highly novel and significant research has been done to develop a complete physically-based theory on the scale invariance and self-similarity of hydrologic processes.

Water resources management involves blending combinations of physical, social, economic, and political science to yield novel insights about the interaction between society and nature that affect societal interests.  HSGG faculty have been leaders in helping California decision makers understand the options and effects of water management schemes, which has also yielded novel scientific advances.  Recently this group has been at the cutting edge of assessing potential climate change effects on water resources and hydro-ecologic modeling in river basin management. Assessment of ecosystem services is a key emerging topic.

Finally, land-atmosphere interactions is investigated by three faculty members and is an emerging topic due to the growing emphasis on climate change research.  Micrometeorology and hydroclimatology are the focal areas of research.  HSGG faculty have a long tradition of research into evapotranspiration that continues to be strong.  A recently added HSGG faculty member is a national leader in global climate modeling  who has highly cited articles addressing the velocity of climate change and high-resolution spatial representation in climate modeling. Last year UC Davis garnered and NSF Integrative Graduate Education and Research Traineeship (IGERT) in Climate Change, Water and Society and also hired a new faculty member in regional climate modeling.  In 2012-13, three of the four LAWR hires (integrated watershed scientist, remote sensing scientist, and hydroclimatologist) will likely conduct research on climate change, among their research portfolios.