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ABSTRACT: The assessment of hydrologic responses to climate change is required in watershed management and planning to protect water resources and environmental quality. This study is designed to evaluate and enhance watershed modeling approach in characterizing climate change impacts on water supply and ecosystem stressors. Soil and Water Assessment Tool (SWAT) was selected as a base model, and improved for the CO2 dependence of potential evapotranspiration and stream temperature prediction. The updated model was applied to quantify the impacts of projected 21st century climate change in the northern Coastal Ranges and western Sierra Nevada, which are important water source areas and aquatic habitats of California. Evapotranspiration response to CO2 concentration varied with vegetation type. For the forest-dominated watersheds in this study, only moderate (1-3%) reductions on evapotranspiration were predicted by solely elevating CO2 concentration under emission scenarios A2 and B1. Modeling results suggested increases in annual average stream temperature proportional to the projected increases in air temperature. Although no temporal trend was confirmed for annual precipitation in California, increases of precipitation and streamflow during winter months and decreases in summers were predicted. Decreased streamflow during summertime, together with the higher projected air temperature in summer than in winter, would increase stream temperature during those months and result in unfavorable conditions for cold-water species. Compared to the present-day conditions, 30-60 more days per year were predicted with average stream temperature >20°C during 2090s. Overall, the hydrologic cycle and water quality of headwater drainage basins of California, especially their seasonality, are very sensitive to projected climate change.
Science of The Total Environment 03/2013; 450-451C:72-82. · 3.29 Impact Factor
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ABSTRACT: Climate change may significantly affect the hydrological cycle and water resource management, especially in arid and semi-arid regions. In this paper, output from the Providing Regional Climates for Impacts Studies (PRECIS) regional climate model were used in conjunction with the Soil and Water Assessment Tool (SWAT) to analyse the effects of climate change on streamflow of the Xiying and Zamu rivers in the Shiyang River basin, an important arid region in northwest China. After SWAT model calibration and validation, streamflow in the Shiyang River Basin was simulated using the PRECIS climate model data for greenhouse gas emission scenarios A2 (high emission rate) and B2 (low emission rate) developed by Intergovernmental Panel on Climate Change. Monthly streamflow and hydrological extremes were compared for present-day years (1961–1990), the 2020s (2011–2040), 2050s (2041–2070) and 2080s (2071–2100). The results show that mean monthly streamflow in Shiyang River Basin generally increased in the 2020s, 2050s and 2080s between 0.7–6.1% at the Zamu gauging station and 0.1–4.8% at the Xiying gauging station. The monthly minimum streamflow increased persistently, but the maximum monthly streamflows increased in the 2020s and slightly decreased in the 2050s and 2080s. This study provides valuable information for guiding future water resource management in the Shiyang River Basin and other arid and semi-arid regions in China.
Hydrological Processes 01/2012; 26:2733–2744. · 2.49 Impact Factor
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ABSTRACT: Estimating groundwater recharge in response to increased atmospheric CO2 concentration and climate change is critical for future management of agricultural water resources in arid or semi-arid regions. Based on climate projections from the Intergovernmental Panel on Climate Change, this study quantified groundwater recharge under irrigated agriculture in response to variations of atmospheric CO2 concentrations (550 and 970ppm) and average daily temperature (+1.1 and +6.4°C compared to current conditions). HYDRUS 1D, a model used to simulate water movement in unsaturated, partially saturated, or fully saturated porous media, was used to simulate the impact of climate change on vadose zone hydrologic processes and groundwater recharge for three typical crop sites (alfalfa, almonds and tomatoes) in the San Joaquin watershed in California. Plant growth with the consideration of elevated atmospheric CO2 concentration was simulated using the heat unit theory. A modified version of the Penman-Monteith equation was used to account for the effects of elevated atmospheric CO2 concentration. Irrigation amount and timing was based on crop potential evapotranspiration. The results of this study suggest that increases in atmospheric CO2 and average daily temperature may have significant effects on groundwater recharge. Increasing temperature caused a temporal shift in plant growth patterns and redistributed evapotranspiration and irrigation water use earlier in the growing season resulting in a decrease in groundwater recharge under alfalfa and almonds and an increase under tomatoes. Elevating atmospheric CO2 concentrations generally decreased groundwater recharge for all crops due to decreased evapotranspiration resulting in decreased irrigation water use. Increasing average daily temperature by 1.1 and 6.4°C and atmospheric CO2 concentration to 550 and 970ppm led to a decrease in cumulative groundwater recharge for most scenarios. Overall, the results indicate that groundwater recharge may be very sensitive to potential future climate changes.
Agricultural Water Management 01/2010; 97(7):1039-1050. · 2.00 Impact Factor
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ABSTRACT: The Soil and Water Assessment Tool (SWAT) was used to assess the impact of climate change on sediment, nitrate, phosphorus and pesticide (diazinon and chlorpyrifos) runoff in the San Joaquin watershed in California. This study used modeling techniques that include variations of CO(2), temperature, and precipitation to quantify these responses. Precipitation had a greater impact on agricultural runoff compared to changes in either CO(2) concentration or temperature. Increase of precipitation by +/-10% and +/-20% generally changed agricultural runoff proportionally. Solely increasing CO(2) concentration resulted in an increase in nitrate, phosphorus, and chlorpyrifos yield by 4.2, 7.8, and 6.4%, respectively, and a decrease in sediment and diazinon yield by 6.3 and 5.3%, respectively, in comparison to the present-day reference scenario. Only increasing temperature reduced yields of all agricultural runoff components. The results suggest that agricultural runoff in the San Joaquin watershed is sensitive to precipitation, temperature, and CO(2) concentration changes.
Environmental pollution (Barking, Essex: 1987) 09/2009; 158(1):223-34. · 3.43 Impact Factor
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ABSTRACT: Quantifying the hydrological response to an increased atmospheric CO2 concentration and climate change is critical for the proper management of water resources within agricultural systems. This study modeled the hydrological responses to variations of atmospheric CO2 (550 and 970 ppm), temperature (+1.1 and +6.4 °C), and precipitation (0%, ±10%, and ±20%) based on Intergovernmental Panel on Climate Change projections. The Soil and Water Assessment Tool (SWAT) was used to model the hydrology and impact of climate change in the highly agricultural San Joaquin watershed in California. This watershed has an area of 14,983 km2 with a Mediterranean climate, resulting in a strong dependence on irrigation. Model calibration (1992–1997) and validation (1998–2005) resulted in Nash–Sutcliffe coefficients of 0.95 and 0.94, respectively, for monthly stream flow. The results of this study suggest that atmospheric CO2, temperature and precipitation change have significant effects on water yield, evapotranspiration, irrigation water use, and stream flow. Increasing CO2 concentration to 970 ppm and temperature by 6.4 °C caused watershed-wide average evapotranspiration, averaged over 50 simulated years, to decrease by 37.5%, resulting in increases of water yield by 36.5%, and stream flow by 23.5% compared to the present-day climate. Increasing temperature caused a temporal shift in plant growth patterns and redistributed evapotranspiration and irrigation water demand earlier in the year. This caused an increase in stream flow during the summer months due to decreased irrigation demand. Water yield, however, decreased with an increase in temperature. Increase of precipitation by ±10% and ±20% generally changed water yield and stream flow proportionally, and had negligible effects on predicted evapotranspiration and irrigation water use. Overall, the results indicate that the San Joaquin watershed hydrology is very sensitive to potential future climate changes. Agricultural implications include changes to plant growth rates, irrigation timing and runoff, all of which may affect future water resources and water quality.
Journal of Hydrology.
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ABSTRACT: Initiated during the late 1970s in China, the Household Responsibility System (HRS) has brought a profound change to the rural economy. The shift from a collective farming system to individually-owned family farms has changed land management practices, affecting both soil quality and agro-environmental sustainability. The purpose of this study was to investigate spatio-temporal variability of soil nutrients influenced by the altered land tenure system, and to evaluate the potential for site-specific management. Using geostatistics and GIS, we characterized the spatial variability of soil nutrients in paddy rice fields in the Hangzhou–Jiaxing–Huzhou watershed, China, following 20 years of altered land management policy. Soil samples, collected in 1982 and 2001, were analyzed for soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK). The spatial variability of each of these soil properties decreased from 1982 to 2001, verifying that the extrinsic factors of the altered land management practices had a weakening effect on the intrinsic factors of soil formation properties. Spatial correlation ranges for SOM, TN, and AP in 2001 all decreased from 1982 with the exception of AK. Temporal geographic maps revealed significant changes in soil nutrient concentrations in the form of increases in SOM, TN, and AP and a sharp decline of AK during the period 1982–2001. This result gave an indication of the imbalance among N, P, and K fertilizers applied in the study area. The results of the comprehensive assessment for current soil nutrients could also, inversely, present challenges for future site-specific management policy on agriculture.
Geoderma.
