Climatic Uncertainties

2011-2012

Research Activities
During the first phase of DCDC, researchers identified and addressed major climatic uncertainties facing Phoenix, including inter-annual drought, climate change, and the urban heat island. We explored the sensitivity of urban water demand to variations in climate to clarify the effect of this uncertainty on our region and its spatiotemporal variability. In DCDC II, we are refining climate and hydrological models to represent the physical characteristics and hydraulic dynamics of our watersheds; to understand and predict the impact of land use and climate change on water supplies; and to inform decision making and climate adaptation strategies.

To accomplish these goals, we added hydrologist Enrique Vivoni to our collaborative group. Vivoni is leading an interdisciplinary team of post-doctoral researchers and graduate students to investigate geographic regions that generate our water supply and the impact of land use/land cover change and climate change scenarios on water supplies and extreme events including floods and droughts. Critical questions guiding this work are: What are the combined effects of climate and land cover change on water supply? Are there tradeoffs in land use management that can mitigate climate impacts on water supplies? This research utilizes a numerical watershed model to explore these tradeoffs and to provide inputs to related DCDC decision-making research.

In one stream of research, Vivoni’s team is using a distributed hydrologic model (TIN-based Real-time Integrated Basin Simulator) to quantify and predict the land surface (or watershed) responses to meteorological forcing by combining meteorological measurements or forecasts and geospatial data into a predictive model. This work uses projections of climate change impacts on streamflow forecasts in Beaver Creek, Arizona. This area is representative of the Salt and Verde River systems as it includes diverse land cover and soil distributions, regional terrain variations in the Mogollon Rim, and hydrologic conditions of both ephemeral and perennial stream flows. Model simulations allow researchers to address climate and land cover changes or manipulations in a spatially-explicit manner to examine runoff generation and streamflow in channels, soil moisture distribution in all landscapes, summer evapotranspiration losses, and recharge of shallow groundwater systems.

In a second line of research, Vivoni’s team is evaluating streamflows during the North American monsoon. The summer monsoon is a significant water supply source and flood hazard in the Salt and Verde River System that has received limited attention. Researchers are conducting simulations using high resolution data in nested watersheds and at forest locations to reproduce the flood hydrograph in the model and compare results from ground data, NEXRAD and NLDAS (satellite) products. The results of this research can inform water managers and other stakeholders about the availability of summer flows for reservoir operations.

Vivoni’s team is also working along with DCDC PI Dave White and researchers from ASU’s Decision Theater and the North American Center for Transborder Studies on a project in cooperation with investigators from the Center for Water in Latin America and the Caribbean (CALCA) at Tecnológico de Monterrey (Tec). This project, which leverages NSF funding with an investment from the FEMSA Foundation, exemplifies our commitment to interdisciplinary research, comparative studies, international collaborations, and science-policy boundary-spanning activities. This project draws upon and extends lessons learned from science-policy engagement in central Arizona to address scientific questions of critical policy importance to multiple stakeholders in Monterrey, Mexico. Hydrologists and social scientists from both Tec and ASU have developed and implemented a stakeholder engagement process to inform modeling efforts. Vivoni’s team is undertaking a reconstruction of a major flood event associated with Hurricane Alex (2010) using meteorological data sets and the outputs from the application of the hydrologic model tRIBS. Modeling activities are focused on scenario building to address impacts of different management decisions, identification of priority conservation areas (PCAs) and future management areas (FMAs).

Moving forward, DCDC will expand our hydrologic research to refine climate and hydrological models, along with parallel stakeholder engagement and science-policy research efforts. In August 2012, we will add two new post-doctoral researchers to support these and related efforts: Hernan Moreno, who is currently completing his Ph.D. under Vivoni’s supervision in the School of Space and Earth Exploration at ASU, and Ted Bohn, who will be joining ASU from the University of Washington. Bohn has received notification of support from NSF for a SEES Fellowship and will work under the direction of Vivoni and White.

DCDC Researchers:

2010-2011

Research Activities
During the initial phase of DCDC, researchers identified and addressed major climatic uncertainties facing Phoenix, including interannual drought, climate change, and the urban heat island. We have explored the sensitivity of urban water demand to variations in climate to clarify the effect of this uncertainty for our region and its spatiotemporal variability. In DCDC II, we are refining climate and hydrological models to represent the physical characteristics and hydraulic dynamics of our watersheds. We will determine the key areas that generate our water supply (what happens if land use/cover changes), the importance of precipitation intensity (what happens to extremes under future climate change), the importance of snow versus rain (what happens to precipitation types under future climate change and what are the impacts on water supply), and the potential effects of changing land-use conditions with wildfires, urban development, and agricultural policies.

In the first year of DCDC II, climate scientist Robert Balling and colleagues continued their successful line of research developing a basic understanding of physical processes that underlie climate and drought conditions in the Southwest. In an article in Theoretical and Applied Climatology, Svoma et al. (2010) developed a high-resolution model for estimating soil moisture for the Salt River Basin. Two articles appeared last year in Physical Geography that used various spatial analytical methods to assess drought trends in the Southwest and conterminous US (Balling and Goodrich 2010; Svoma and Balling 2010). In an article in Theoretical and Applied Climatology, Balling and Goodrich (2011) examined variations and trends in precipitation intensity in the conterminous US.

In a second line of climatic-uncertainties research supported under DCDC II, climatologists Andrew Ellis and Robert Balling and their team worked closely with Water Resource Operations personnel from Salt River Project (SRP) to assess how projected changes in runoff under various climate-change scenarios might threaten surface-water replenishments of the SRP reservoir system. They developed and authored a reservoir simulation model (ResSim; FORTRAN programming language on a UNIX platform) incorporating the same parameters and operational guidelines as embodied in the SRP Long-Term Drought Planning Model (LTDPM), allowing efficient exploration of many climate and runoff scenarios. This collaboration resulted in supplementary funding from SRP to test the model using historical data and compare with LTDPM results, confirming equivalent ability to reflect key periods of drought vulnerability.

DCDC Researchers: