Dongguo Shao

Bio: Dongguo Shao is an academic researcher from Wuhan University. The author has contributed to research in topics: Environmental science & Water quality. The author has an hindex of 16, co-authored 35 publications receiving 729 citations.

Effects of alternate wetting and drying irrigation on percolation and nitrogen leaching in paddy fields

Abstract: The widely adopted alternate wetting and drying (AWD) irrigation for rice production is increasingly needed to quantify the different water outflows and nitrogen leaching losses We investigated the effects of AWD on percolation, water productivity, nitrogen leaching losses, and nitrogen productivity through in situ experiments Results show that AWD reduced irrigation water without a significant impact on grain yields and increased the mean water productivity by 169 % compared with continuously flood irrigation (CFI) The mean nitrogen productivity of 135 kg ha−1 N level was 222 % higher than that of 180 kg ha−1 N level, although grain yields substantially increased because of nitrogen fertilization application The percolation was also reduced by 153 % in 2007 and 83 % in 2008 compared to CFI However, the cumulative percolation of the first 5 days after irrigation in AWD plots is significantly larger than that in CFI plots The NH4+–N and TN leaching losses of AWD and CFI had no significant variations while the NO3−–N leaching losses were increased caused by AWD The total NH4+–N, NO3−–N, and TN leaching losses of AWD in the first 3 days after irrigation were higher than that of contemporaneous CFI The results indicate that the bypass or preferential flow and strengthened nitrification–denitrification nitrogen transformation processes because of alternate wetting and drying potentially decrease the water saving effectiveness and increase the NO3−–N loading to the groundwater

Risk Evaluation of Water Shortage in Source Area of Middle Route Project for South-to-North Water Transfer in China

Abstract: Water diversion causes changes in the downstream flow regime, which may intensify the crisis of water shortage. The effect of the diversion on water shortage depends on the volumes of water transferred and water demand of source area, the upstream inflow and the way the reservoir is operated. This paper reports the findings of a study to assess the impact of water diversion from Danjiangkou reservoir on middle and lower Hanjiang River, part of the source area of South-to-North Water Transfer Project, China. The risk evaluation model consists of four parts, including inflow generation, water demand, simulation, and performance evaluation. Thomas–Fiering model and Mont-Carlo method are utilized to simulate monthly reservoir inflow data and a 12-dimensional random vector is used to describe the 12-month water demand in middle and lower Hanjiang River. A reservoir simulation model is established for optimum operation of Danjiangkou reservoir. Several scenarios including different water diversion scales are run by the risk evaluation model, whose outputs provide valuable information for decision making.

Assessment of CFSR, ERA-Interim, JRA-55, MERRA-2, NCEP-2 reanalysis data for drought analysis over China

Abstract: Five reanalysis datasets—National Centers for Environmental Prediction reanalysis II (NCEP-2), NCEP Climate Forecast System Reanalysis (CFSR), European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim), Japanese 55-year Reanalysis Project (JRA-55), and National Aeronautics and Space Administration (NASA) Modern Era Reanalysis for Research and Applications Version-2 (MERRA-2)—are selected to estimate meteorological droughts of China using three drought indices—the Palmer Drought Severity Index (PDSI), Standardized Precipitation Index (SPI), and Standardized Precipitation Evapotranspiration Index (SPEI). Drought indices, drought areas and drought severity estimated for China from these reanalysis datasets are assessed against corresponding results obtained from observed climate dataset of China using Nash–Sutcliffe efficiency (NSE), correlation coefficient, and the analysis of time series. Further, temperature, precipitation and potential evapotranspiration data of the five reanalysis datasets are also compared against the observed dataset. Drought indices and drought areas estimated from reanalysis datasets are generally more representative of historical droughts that had occurred in eastern China than in western China. However, the performance of these five reanalysis datasets in representing the drought severity is unsatisfactory in both western China and eastern China. SPEI is generally more representative than PDSI and SPI partly because temperature and potential evapotranspiration data of reanalysis datasets are generally better than precipitation data. PDSI is also based on a supply-and-demand model of soil moisture but estimating the demand of soil moisture is complicated. Therefore, SPEI is preferred over PDSI and SPI as the drought index to characterize the meteorological droughts of China. Climate data and meteorological drought characteristics of eastern China are best represented by JRA-55, while that of western China are best represented by MERRA-2. From 1980 to 2014, statistically significant increasing trends in annual drought areas and drought severity are detected from JRA-55 and observed climate datasets in eastern China, but they are only detected from observed dataset in western China.

Simplified evaporation method for determining soil hydraulic properties: a reinvestigation of linearization errors

Abstract: Accurate knowledge of the soil hydraulic properties is a prerequisite for reliable modelling of soil water dynamics. As a consequence, many methods have been developed to derive these constitutive relationships either under field or laboratory conditions. Among these methods, the simplified evaporation method conducted on soil samples in the laboratory has found widespread use and application, mainly due to its relative ease of implementation and its straightforward evaluation of the experimental data. This method, however, relies on various simplifying assumptions. A common approach to assess the validity of these assumptions and to explore potential linearization errors associated with them is the use of synthetic data. In the past, such synthetic data were generated using rather simplistic models considering liquid water flow in capillaries only. In this study, we reinvestigated the accuracy of the simplified evaporation method using a more realistic process description of evaporative drying of the soil sample, including both liquid water flow in capillaries and films, as well as isothermal water vapour diffusion. In contrast to previous results reported in the literature, our results show that the simplifying assumptions used to evaluate the experimental data may result in biased estimates of the soil hydraulic properties, particularly for coarse textured soils. The bias typically increased progressively during stage-two evaporation, which is characterized by the development of a dry surface layer in which water flow is dominated by diffusion of water vapour, resulting in strongly nonlinear pressure head and water content profiles. We investigated various strategies for correcting for this bias caused by simplifying assumptions.