Lakes and reservoirs are important components of freshwater. The expansion and shrinkage of lakes/reservoirs may alter meteorological characteristics and the underlying surface conditions, which would further affect energy and water vapor fluxes in the surrounding area. In this study, the expansion and shrinkage of the Guanting Reservoir during 2013-2017 was analyzed using remote sensing data. Data collected from the Huailai Remote Sensing Experiment Station were used to analyze the energy and water vapor fluxes. The results showed the annual expansion of the Guanting Reservoir from 2013 to 2017, and a seasonal variation characterized by expansion in spring, shrinkage in summer and autumn, and expansion again in winter was exhibited. Meanwhile, the evapotranspiration (ET) in the surrounding area also increased annually. In the growing season, the seasonal shrinkage of the reservoir indirectly affected ET through net radiation, deep soil moisture and vegetation growth conditions, while in the non-growing season, the seasonal expansion directly increased ET by increasing the proportion of water bodies in the source area and increased net radiation and surface soil moisture. In addition, with the reservoir expanding year by year, the difference in ET between the closer site and further site from the reservoir increased obviously, especially in the non-growing season during the seasonal expansion of the reservoir. The results help with the ecosystem restoration and sustainable development of lakes/reservoirs in arid and semiarid areas.

The vast Karst area in southwestern China is ecologically fragile region, where both soil organic carbon (SOC) and total nitrogen (TN) are evidently sensitive to LUCC. However, there has not been any comprehensive study to analyze the effects of LUCC on SOC/TN in this region based on large data ensembles. In this paper, the response of SOC and TN storage to LUCC (i.e., deforestation and land restoration) in the Karst region of southwestern China was investigated by meta-analysis, which was found to be controlled by a series of impact factors, such as the type of LUCC, sampling depth, calculation methods and environmental factors. Based on 471 sets of SOC data and 468 sets of TN data, Firstly, we evaluated the calculation methods (i.e., fixed-depth method, the main deviation from the two methods was that the FD procedure neglected the heterogeneity of soil bulk density, which may underestimate the loss of SOC and TN after deforestation but overestimate the benefits of land restoration to SOC and TN. Secondly, we found that when woodland and grassland were converted to cultivated land or other land types, SOC and TN losses were greater; while other LUCCs had less impact. Similarly, land restoration increased the SOC and TN, especially the restoration from farmland to forests. Also, we demonstrated that increasing the soil sampling depth could significantly alter the response of SOC and TN to LUCC. Finally, the environmental factors affecting SOC storage (such as soil properties, geographic and climatic factors and duration) were discussed.

Based on the integrated ParFlow.CLM modeling in the Little Washita basin located in the southwestern Oklahoma in the U.S., the long-term effects of groundwater (GW) pumping on ground surface temperature (GST) are studied. Conclusions are obtained based on the simulation results as follows. The subsurface can be conceptualized as a buffer on variations of GST while GW pumping can weaken this buffer causing hotter summer and colder winter. In the long-term pumping, the variations of GST (ΔGST) present nonlinear warming trend in average by rapidly increasing in the beginning and gradually reaching dynamic equilibrium. This is due to the attainment of a new equilibrium of the GW flow system with a sustainable pumping rate. Whereas, for unsustainable pumping, it is mainly attributed to the fact that the water table depth finally becomes lower than the critical depth range (1–10 m). Different coupling depths between ParFlow and CLM are tested in the long-term pumping scenarios since it determines the heat capacity of the subsurface buffer which is important on regulating GST. The buffer with deeper coupling depth is more effective on damping the nonlinearity and the amplitude of ΔGST. In addition, the effects of coupling depth on GST are more prominent when pumping occurs due to the degenerated thermal properties. In other words, the time-scale for GST to response the different coupling depth is greatly shortened under pumping in contrast to natural state. This study diagnosed the subsurface buffer on variations of GST with the role of coupling depth in the integrated modeling under long-term GW pumping. The results are expected to have implications on integrated modeling in GW depletion areas worldwide.