Ms.Yi published a study in Water Resources Research(Volume59, Issue3 March 2023e2022WR032415).Grain for Green project could result in high evapotranspiration (ET), exacerbate water shortage, and intensify conflicts in water demand between ecosystems and humans in many water-limited areas. However, it is still unclear how vegetation restoration would influence ET in humid karst regions where abundant precipitation but quick leakage. Particularly, it is challenging that existing ET measurement methods are not applicable simultaneously for various ecosystems in such highly heterogeneous and fragmented landscapes.To solve this issue, this study, for the first time, develops a new ET measurement system, by integrating multi-techniques, to quantify ET for multiple vegetation restoration types and identify their controlling factors in a humid karst region for three consecutive years (Figure 1).The results show that (1) for different succession stages during natural restoration, the ET of secondary forest (680 ± 7 mm yr-1) > shrub (564 ± 16 mm yr-1) > grass (546 ± 12 mm yr-1) > cropland (513 ± 8 mm yr-1) (P < 0.05)(Figure 2); (2) ET of all ecosystems are far less than that of precipitation (1059 ± 63 mm yr-1) but closer to potential ET (849 ± 11 mm yr-1), and soil moisture has been maintained at > 0.20 cm3cm-3 in the growing season; (3) solar radiation and vapor pressure deficit are the two predominant factors on the ET (P <0.01), while there is no significant relationship between ET and soil moisture (P >0.05). The results suggest that vegetation restoration returned from cropland in humid karst regions increased ET but may not induce water scarcity for vegetation sustainability, at least under normal climatic conditions. As vegetation restoration could consume more than half of annual precipitation, future research should pay more attention on ecosystem adaptive managements in response to increasing drought extremes under global warming.

https://doi.org/10.1029/2022WR032415

Mr.Yang published a study in Hydrological Processes( 2022.12, 36(12)).This study explores the potential of estimating hydrological components (runoff, ET, TWSC, groundwater, and root-zone water storage.) using a conceptual model driven and calibrated by multisource remote sensing data only. The performances of the model were evaluated in 13 catchments with different geological, climatic and vegetation conditions. Results show that the model was encouraging in simulating monthly runoff (median KGE, 0.71; RMSE, 19.4 mm/mon), ET (median KGE, 0.86; RMSE, 9.0 mm/mon), and TWSC (median KGE, 0.58; RMSE, 26.6 mm/mon). The good positive correlation between root-zone water storage and gross primary productivity also indicates the effectiveness of the model in simulating root-zone water storage.

https://doi.org/10.1002/hyp.14773

Mr.Liu published a study in Journal of Hydrology (2016, 535: 173-180).This study investigated the effects of karst landform on the elasticity of actual evapotranspiration (derived by the Budyko equation), estimated the contribution of climate change and evaluated the implications, on the basis of 13 typical catchments that have different karst landform coverages in southwest China. The results indicate that portion of karst landform (POK) is the most influencing factor for the elasticity of actual evapotranspiration in this region. Moreover, the actual evapotranspiration in karst catchments is more sensitive to precipitation change and less sensitive to the potential evapotranspiration change than that in the non-karst catchments. On the other hand, the contribution of climate change to actual evapotranspiration was generally negative in this region.

https://www.researchgate.net/publication/293016981 

Ms. Yang published a study in Soil & Tillage Research (2016, 157: 83–92 ) in this days. She investigated the grass cultivation and field management on the soil hydraulic properties in karst region in SW China, including the soil field-saturated hydraulic conductivity (Kfs) and the water retention parameter (a). Results showed that the farming practices (nitrogen fertilization, cutting frequency and cutting intensity) of Napier grass had higher influence on the soil hydraulic properties of the topsoil than those of the subsoil; nitrogen fertilization influenced the soil hydraulic properties more significantly than cutting frequency and cutting intensity. The Kfs of the topsoil generally decreased with increasing nitrogen fertilization and cutting frequency. This study suggests that the implementation of different farming practices differently alters soil hydrologic functions. 

http://www.sciencedirect.com/science/article/pii/S0167198715300647

By using the techniques of overlapping moving windows, the Mann-Kendall trend test, correlation, and stepwise regression, Dr. Liu examined the spatial temporal variation of precipitation extremes and investigated the potential key factors influencing this variation in southwestern (SW) China. Results showed that the changing trends of precipitation extremes were not spatially uniform, but the spatial variability of these precipitation extremes decreased from 1959 to 2012. Further analysis found that atmospheric circulations rather than local factors (land cover, topographic conditions, etc.) were themain cause

of such precipitation extremes. This study suggests that droughts or floods may become more homogenously widespread throughout SW China.

http://onlinelibrary.wiley.com/doi/10.1002/2014JD022886/full

Climate extremes have and will continue to cause severe damages to buildings and natural environments around the world. A full knowledge of the probability of the climate extremes is important for the management and mitigation of natural hazards. Southwestern China is a sensitive region for climate change due to its geographic, ecological and social background. There have been also many studies that focused on the change of climate extremes in southwestern China, but most of these studies focused on the changing patterns of several climate extreme indices, and have not found any significant changing trends, except few climate extreme indices. Hence, the insignificant changing trends in climate extremes alone could not adequately explain the more frequent droughts and floods in southwestern China, the probability of occurrence should be important.

Based on Mann–Kendall trend test and copulas, this paper investigated the characteristics of precipitation extremes as well as their implications in southwestern China (Yunnan, Guangxi and Guizhou Province), through analyzing the changing trends and probabilistic characteristics of six indices. Results showed that the study area had generally become drier and experienced enhanced precipitation extremes. Relatively higher risk of drought in Yuanan and flood in Guangxi was observed, respectively. However, the changing trends of the precipitation extremes were not spatially uniform: increasing risk of extreme wet events for Guangxi and Guizhou, and increasing probability of concurrent extreme wet and dry events for Yunnan. Meanwhile, trend analyses of the 10 year return levels of the selected indices implied that the severity of droughts decreased in Yunnan but increased significantly in Guangxi and Guizhou, and the severity of floods increased in Yunnan and Guangxi in the past decades. 

http://iopscience.iop.org/1748-9326/9/6/064002/

Quantifying partitioning of precipitation into evapotranspiration (ET) and runoff is the key to assessing water availability globally. Dr. Xu developed a universal model to predict water-energy partitioning (ϖ parameter for the Fu’s equation, one form of the Budyko framework) which spanned small to large scale basins globally.

In this study, a neural network model was developed using a data set of 224 small U.S. basins (100–10,000 km2) and 32 large, global basins (~230,000–600,000 km2) independently and combined based on both local and global factors. The Budyko framework with NN estimated ϖ reproduced observed mean annual ET well for the combined 256 basins. The predicted mean annual ET for ~36,600 global basins is in good agreement (R2 = 0.72) with an independent global satellite-based ET product, inversely validating the NN model. The NN model enhances the capability of the Budyko framework for assessing water availability at global scales using readily available data.

http://onlinelibrary.wiley.com/doi/10.1002/2013GL058324/abstract

 New paper publicated in Jounal of Hydrology (2013)

In this study, Dr. Xu assessed the potential impacts of biofuel production on water resources by exploring relationships between hydrologic changes and climate and land surface changes based on long-term stream gage and climate data. He pointed out the importance of land surface changes on hydrology, and suggested that any future land surface changes, should consider impacts on the hydrology.