Modeling the Hydrology of Climate Change in California’s Sierra Nevada for Subwatershed Scale Adaptation¹

Abstract

Young, Charles A., Marisa I. Escobar‐Arias, Martha Fernandes, Brian Joyce, Michael Kiparsky, Jeffrey F. Mount, Vishal K. Mehta, David Purkey, Joshua H. Viers, and David Yates, 2009. Modeling the Hydrology of Climate Change in California’s Sierra Nevada for Subwatershed Scale Adaptation. Journal of the American Water Resources Association (JAWRA) 45(6):1409‐1423. Abstract: The rainfall‐runoff model presented in this study represents the hydrology of 15 major watersheds of the Sierra Nevada in California as the backbone of a planning tool for water resources analysis including climate change studies. Our model implementation documents potential changes in hydrologic metrics such as snowpack and the initiation of snowmelt at a finer resolution than previous studies, in accordance with the needs of watershed‐level planning decisions. Calibration was performed with a sequence of steps focusing sequentially on parameters of land cover, snow accumulation and melt, and water capacity and hydraulic conductivity of soil horizons. An assessment of the calibrated streamflows using goodness of fit statistics indicate that the model robustly represents major features of weekly average flows of the historical 1980‐2001 time series. Runs of the model for climate warming scenarios with fixed increases of 2°C, 4°C, and 6°C for the spatial domain were used to analyze changes in snow accumulation and runoff timing. The results indicated a reduction in snowmelt volume that was largest in the 1,750‐2,750 m elevation range. In addition, the runoff center of mass shifted to earlier dates and this shift was non‐uniformly distributed throughout the Sierra Nevada. Because the hydrologic model presented here is nested within a water resources planning system, future research can focus on the management and adaptation of the water resources system in the context of climate change.

Modeling of Andean Páramo Ecosystems’ Hydrological Response to Environmental Change

“…These types of assumptions generalize the hydrological responses of land covers, their soil types, physical soil properties, terrain characteristics, etc. The assumptions are well documented and defensible with peer-reviewed literature [19][20][21][22]34].…”

“…The process for defining the catchments, including size and land use type, within the Quiroz-Chipillico watershed model followed the same methodology described by [22]. It consists of four steps: (1) delineation of watersheds and elevation bands using a DEM; (2) intersection of elevation bands with watersheds to create WEAP catchments; (3) classification of vegetation; and (4) intersection of vegetation, and watersheds to calculate fractional areas for each vegetation combination in each catchment node.…”

“…The historic time series were 20 years long; therefore to create a 50-year time series, data values were repeated every 20 years until a 50-year time series was completed. To simulate warmer and drier scenarios, the daily and monthly Quiroz-Chipillico watershed models followed [22] to create a precipitation and temperature forcing method. This produced time series of future climate data using a delta value, a constant value applied to the time series data in order to increase or decrease the values in a monthly and daily time step, respectively, for the watershed land surrounding the páramo up to the closing point in the downstream watershed.…”

Integrated assessment of policy interventions for promoting sustainable irrigation in semi-arid environments: A hydro-economic modeling approach

“…FoUowing recent WEAP applications (Purkey et al, 2008;Young et al, 2009), catchment units were delineated, using a 90 m SRTM Digital Elevation Model and watershed pour points, and populated with spatially distributed climate and land cover data obtained from IGN (2004) and Mitchell and Jones (2005).…”

Conjunctive surface water and groundwater management under climate change

“…Local water yield, evapotranspiration, irrigation water use, and stream flow would be significantly affected by projected changes of atmospheric CO 2 , temperature, and precipitation. Young et al (2009) evaluated the hydrological effects of climate change on snow pack and initiation of snowmelt in the Sierra Nevada in California, covering watersheds from the Feather River in the north to the Kern River in the south. A reduction in snow pack was found, resulting in a shift in runoff center of mass to earlier dates.…”