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Analysis with the integrated South Platte assessment model to assess the sensitivity of the WWA user community to the stresses of climate variability and regional growth
Team members: Lee Rozaklis, Andy Barrett, Chuck Howe, Chris Goemans, Jim Saunders
We are conducting a set of sensitivity experiments with an integrative assessment model to assess the impacts of climate variability and regional growth on water shortages in various sectors. Our intent is to identify the sectors of the WWA user community within the South Platte who are most sensitive to climate variability. We also plan to use the South Platte Assessment model to examine the effects of climate variability and regional growth on the relative proportion of runoff that is derived from return flows, and the associated impacts on water quality.
South Platte Model
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Our approach to integrated modeling of the South Platte water supply and allocation system is described in the figure above. The model provides a simplified representation of water supply, water demand, and water storage, allocation and management for all of the major tributaries of the South Platte basin, and, thus, offers a quantitative framework to assess the impacts of climate variability and regional growth on water shortages. For model input, the model only requires monthly stream flow estimates for each of the 23 headwater basins, as well as estimates of population and irrigated acreage. Stream flow inputs are estimated using a simple monthly water balance model, driven by temperature and precipitation data from stations in and around the South Platte basin. The Assessment model is spatially explicit and allows us to differentiate between water shortages in cities and in agriculture. Assessment of the relative proportion of runoff that is derived from return flows allows us to identify impacts on water quality. |
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Sensitivity Experiments
We are conducting a set of sensitivity experiments with the Assessment model to assess the impacts of climate variability and regional growth on water shortages in various sectors. Our sensitivity experiments first use climate "slices" from the historical record (e.g., drought periods in the 1930s and the 1950s) to examine the impact of climate variability on modeled water levels in various reservoirs, modeled stream flow at various nodes in the South Platte, and modeled water shortages in municipal and agricultural sectors. We then turn to longer time-scales of variability, and use downscaled output from long integrations of climate models and paleo-climatic reconstructions to estimate stream flow at each of the model input nodes. In this way, we translate our best estimates of the probability of drought into estimates of the probability of water shortages in different sectors. Our intent is to identify the sectors of the WWA user community within the South Platte who are most sensitive to climate variability. To assess the impacts of regional growth, we are running the Assessment model using estimates of population and irrigated acreage at a given time in the future (e.g., 2040), and comparing this model run with current levels of population and irrigated acreage. This helps us define the effects of regional growth on climate vulnerability, and, with an understanding of the effects of climate stresses, if regional growth will cause some sectors of the water community in the South Platte to become less resilient to climate variability. Results coming soon!