This paper combines environmental science, inorganic chemistry, water quality monitoring and other disciplines to analyze and assess the heavy metals in the water bodies and sediments of the Fenghe River Basin (FRB) in Shaanxi Province, and reveal their sources. Water Quality Index (WQI), Nemero Index (Pn), Geological Accumulation Index (I-geo) and Potential Ecological Risk Index (RI) are used to assess heavy metals in water and sediments. Pearson correlation analysis (CA), hierarchical cluster analysis (HCA), principal component analysis (PCA) and positive matrix factorization (PMF) models are used to study the relationship and source of heavy metals. The results show that most of the residual heavy metals in the water are below the corresponding environmental quality standards for surface water. Most of the heavy metals in the sediment exceed the background value of the soil.The factors or sources of heavy metals in water and sediment are revealed in detail through PMF models. The main sources of pollution in the region are urban construction and transportation, electronics industry, machinery manufacturing and tourism. In water, the average contribution rates of these four sources to heavy metals were 36.8%, 11.7%, 9.4% and 42.0%, and in sediments were 8.0%, 29.2%, 23.9% and 38.9%. Therefore, these sectors should be given sufficient attention.

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X. 2011. Development and testing of a remote sensing-based model for estimating groundwater levels in aeolian desert areas of China. Can. J. Soil Sci. 91: 29Á37. Regional groundwater level is an important data set for understanding the relationships between groundwater resources and regional ecological environments. The decline in water table levels leads to vegetation degradation and thus affects the ecological environment. Such a negative effect is especially apparent in the desertification areas. In this study, a remote-sensing based method was proposed to predict the distribution of the regional groundwater level in an aeolian desert area in northern China. The study used the Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing data and field investigations. Based on field investigation of groundwater level, soil moisture, and other supporting information in the aeolian desert area, as well as the soil moisture distribution derived from the MODIS images, empirical equations describing the relationship between the soil moisture and groundwater level were obtained. The groundwater levels derived using the MODIS image data were verified by groundwater levels measured from 58 wells. The results show that the correlation coefficient between the measured groundwater levels and the remote sensing-based estimated water levels was 0.868, indicating that the error is small and the predictions closely reflect the real water levels. This model can be used to predict groundwater levels in aeolian desert areas based on remote sensing data sets.

Assessing the impacts of climate change on hydrological regime and associated social and economic activities (such as farming) is important for water resources management in any river basin. In this study, we used the popular Soil and Water Assessment Tool (SWAT) to evaluate the impacts of future climate change on the availability of water resources in the Heihe River basin located within Shaanxi Province, China, in terms of runoff and streamflow. The results show that over the next 40 years (starting in 2020 till 2059), changes in the averaged annual runoff ratio are approximately [Formula: see text]11.0%, [Formula: see text]6.4%, 7.2%, and 20.4% for each of the next four consecutive decades as compared to the baseline period (2010–2019). The predicted annual runoff demonstrates an increase trend after a reduction and may result in increased drought and flood risk in the Heihe River basin. To minimize or mitigate these impacts, various adaptation methods have been proposed for the study area, such as stopping irrigation, flood control operation; reasonable development and utilization of regional underground water sources should be implemented in Zhouzhi county and Huyi region in the lower reaches of Heihe River basin.

The likelihood of future global water shortages is increasing and further development of existing operational hydrologic models is needed to maintain sustainable development of the ecological environment and human health. In order to quantitatively describe the water balance factors and transformation relations, the objective of this article is to develop a distributed hydrologic model that is capable of simulating the surface water (SW) and groundwater (GW) in irrigation areas. The model can be used as a tool for evaluating the long-term effects of water resource management. By coupling the SWAT and MODFLOW models, a comprehensive hydrological model integrating SW and GW is constructed. The hydrologic response units for the SWAT model are exchanged with cells in the MODFLOW model. Taking the Heihe River Basin as the study area, 10 years of historical data are used to conduct an extensive sensitivity analysis on model parameters. The developed model is run for a 40-year prediction period. The application of the developed coupling model shows that since the construction of the Heihe reservoir, the average GW level in the study area has declined by 6.05 m. The model can accurately simulate and predict the dynamic changes in SW and GW in the downstream irrigation area of Heihe River Basin and provide a scientific basis for water management in an irrigation district.

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The utilization of aquifer energy is a new technology closely related to the development of injection and production well technologies. Accurately predicting the effective use of geothermal energy storage in a surrounding aquifer is of great significance. A developed theory of groundwater hydro-geothermal transfer is suggested by analyzing the general features of stored energy in aquifers together with the interactions between flow connections and thermal breakthroughs. Based on the water-heat transfer in an aquifer, a coupled numerical model of groundwater flow and heat transfer is established using FEFLOW software for an injection and production wells system in the city of Xianyang to simulate the flow and temperature field. The results show that the key for the formation of a flow connection is the hydraulic gradient. That is, whether the flow connection will occur can be judged quantitatively according to the hydraulic gradient. Flow connections occur more easily through greater flow quantities and quicker injection and pumping rates, which lead to earlier occurrences of thermal breakthroughs. At an operation time of 120 days, to prevent thermal breakthroughs in the production wells, the reasonable well spacing was between 180 and 200 m, and the optimal well spacing was 180 m. This method is of great

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