Northern China is one of the most densely populated regions in the world. Agricultural activities have intensified since the 1980s to provide food security to the country. However, this intensification has likely contributed to an increasing scarcity in water resources, which may in turn be endangering food security. Based on in-situ measurements of soil moisture collected in agricultural plots during 1983–2012, we find that topsoil (0–50 cm) volumetric water content during the growing season has declined significantly (p < 0.01), with a trend of −0.011 to −0.015 m3 m−3 per decade. Observed discharge declines for the three large river basins are consistent with the effects of agricultural intensification, although other factors (e.g. dam constructions) likely have contributed to these trends. Practices like fertilizer application have favoured biomass growth and increased transpiration rates, thus reducing available soil water. In addition, the rapid proliferation of water-expensive crops (e.g., maize) and the expansion of the area dedicated to food production have also contributed to soil drying. Adoption of alternative agricultural practices that can meet the immediate food demand without compromising future water resources seem critical for the sustainability of the food production system.

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Northern Eurasian ecosystems play an important role in the global climate system. Northern Eurasia (NE) has experienced dramatic climate changes during the last half of the 20th century and to present. To date, how evapotranspiration (ET) and water availability (P-ET, P: precipitation) had changed in response to the climatic change in this region has not been well evaluated. This study uses an improved version of the Terrestrial Ecosystem Model (TEM) that explicitly considers ET from uplands, wetlands, water bodies and snow cover to examine temporal and spatial variations in ET, water availability and river discharge in NE for the period 1948-2009. The average ET over NE increased during the study period at a rate of 0.13 mm year(-1) year(-1). Over this time, water availability augmented in the western part of the region, but decreased in the eastern part. The consideration of snow sublimation substantially improved the ET estimates and highlighted the importance of snow in the hydrometeorology of NE. We also find that the modified TEM estimates of water availability in NE watersheds are in good agreement with corresponding measurements of historical river discharge before 1970. However, a systematic underestimation of river discharge occurs after 1970 indicates that other water sources or dynamics not considered by the model (e.g., melting glaciers, permafrost thawing and fires) may also be important for the hydrology of the region

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