Assessing the impact of human interventions on floods and low flows in the Wei River Basin in China using the LISFLOOD model
Gai, Lingtong ; Nunes, João P. ; Baartman, Jantiene E.M. ; Zhang, Hongming ; Wang, Fei ; Roo, Ad de; Ritsema, Coen J. ; Geissen, Violette - \ 2019
Science of the Total Environment 653 (2019). - ISSN 0048-9697 - p. 1077 - 1094.
Flood return period - Hydrological model - Land use - LISFLOOD - Reservoir - Water diversion
Floods are extreme hydroclimatic events that threaten societies and ecosystems. The effects of these events are greatly influenced by the changes that humans have imposed on the environment. The LISFLOOD model is a physically based rainfall-runoff model that simulates the hydrological processes in a catchment. Using globally available land cover, soil, and vegetation as well as meteorological and geographical datasets as input, the LISFLOOD model has the potential to be applied worldwide, even for regions where data are lacking. This study first calibrated and validated the LISFLOOD model in the Wei River Basin in China (432,000 km2) for the years between 2000 and 2010 at 0.05° resolution with a monthly Nash-Sutcliffe model efficiency coefficient of 0.79 at the Huaxian station located at the catchment outlet. The outlets of 17 tributaries draining into the main river were then identified in order to assess the contribution of each tributary to the total runoff occurring as a result of flooding. Four categories of scenarios focusing on human interventions in the basin were created and evaluated: 1) Business as usual, 2) Additional reservoirs constructed in different catchments, 3) Land use as in 1980, and 4) Water diversion plan with a pipeline injection of a fixed daily inflow from an adjacent catchment. The results of the scenarios are presented for three strategically important cities located on the floodplain. In general, the construction of the reservoirs could have an effect on reducing peak flows and decreasing the flood return periods while increasing the low flows. The water diversion plan scenarios increased the low flow by 41 times averaged for the three cities. In conclusion, the LISFLOOD model is a sophisticated model for land and water management planning on the catchment scale for reducing the effects of flood and drought.
Influence of microplastic addition on glyphosate decay and soil microbial activities in Chinese loess soil
Yang, Xiaomei ; Bento, Célia P.M. ; Chen, Hao ; Zhang, Hongming ; Xue, Sha ; Lwanga, Esperanza H. ; Zomer, Paul ; Ritsema, Coen J. ; Geissen, Violette - \ 2018
Environmental Pollution 242 (2018). - ISSN 0269-7491 - p. 338 - 347.
Glyphosate - Microplastic - Pesticide decay - Soil microbial activities - Soil quality
The intensive use of pesticide and plastic mulches has considerably enhanced crop growth and yield. Pesticide residues and plastic debris, however, have caused serious environmental problems. This study investigated the effects of the commonly used herbicide glyphosate and micrometre-sized plastic debris, referred as microplastics, on glyphosate decay and soil microbial activities in Chinese loess soil by a microcosm experiment over 30 days incubation. Results showed that glyphosate decay was gradual and followed a single first-order decay kinetics model. In different treatments (with/without microplastic addition), glyphosate showed similar half-lives (32.8 days). The soil content of aminomethylphosphonic acid (AMPA), the main metabolite of glyphosate, steadily increased without reaching plateau and declining phases throughout the experiment. Soil microbial respiration significantly changed throughout the entirety of the experiment, particularly in the treatments with higher microplastic addition. The dynamics of soil β-glucosidase, urease and phosphatase varied, especially in the treatments with high microplastic addition. Particles that were considerably smaller than the initially added microplastic particles were observed after 30 days incubation. This result thus implied that microplastic would hardly affect glyphosate decay but smaller plastic particles accumulated in soils which potentially threaten soil quality would be further concerned especially in the regions with intensive plastic mulching application. Microplastic hardly affected herbicide glyphosate decay in soil but soil microbial activities which, in turn, would indirectly influence pesticide behaviour in soil ecosystem.
An improved method for calculating slope length (λ) and the LS parameters of the Revised Universal Soil Loss Equation for large watersheds
Zhang, Hongming ; Wei, Jicheng ; Yang, Qinke ; Baartman, Jantiene E.M. ; Gai, Lingtong ; Yang, Xiaomei ; Li, Shu Qin ; Yu, Jiantao ; Ritsema, Coen J. ; Geissen, Violette - \ 2017
Geoderma 308 (2017). - ISSN 0016-7061 - p. 36 - 45.
GIS - LS - RUSLE - Soil erosion - Terrain analysis
The Universal Soil Loss Equation (USLE) and its revised version (RUSLE) are often used to estimate soil erosion at regional landscape scales. USLE/RUSLE contain parameters for slope length factor (L) and slope steepness factor (S), usually combined as LS. However a major limitation is the difficulty in extracting the LS factor. Methods to estimate LS based on geographic information systems have been developed in the last two decades. L can be calculated for large watersheds using the unit contributing area (UCA) or the slope length (λ) as input parameters. Due to the absence of an estimation of slope length, the UCA method is insufficiently accurate. Improvement of the spatial accuracy of slope length and LS factor is still necessary for estimating soil erosion. The purpose of this study was to develop an improved method to estimate the slope length and LS factor. We combined the algorithm for multiple-flow direction (MFD) used in the UCA method with the LS-TOOL (LS-TOOLSFD) algorithms, taking into account the calculation errors and cutoff conditions for distance, to obtain slope length (λ) and the LS factor. The new method, LS-TOOLMFD, was applied and validated in a catchment with complexly variable slopes. The slope length and LS calculated by LS-TOOLMFD both agreed better with field data than with the calculations using the LS-TOOLSFD and UCA methods, respectively. We then integrated the LS-TOOLMFD algorithm into LS-TOOL developed in Microsoft's.NET environment using C# with a user-friendly interface. The method can automatically calculate slope length, slope steepness, L, S, and LS factor, providing the results as ASCII files that can be easily used in GIS software and erosion models. This study is an important step forward in conducting accurate large-scale erosion evaluation.
An integrated algorithm to evaluate flow direction and flow accumulation in flat regions of hydrologically corrected DEMs
Zhang, Hongming ; Yao, Zhihong ; Yang, Qinke ; Li, Shuqin ; Baartman, Jantiene E.M. ; Gai, Lingtong ; Yao, Mingtian ; Yang, Xiaomei ; Ritsema, Coen J. ; Geissen, Violette - \ 2017
Catena 151 (2017). - ISSN 0341-8162 - p. 174 - 181.
Channel networks - Flat area - Flow accumulation - Flow direction - Hydrology
In order to conduct an accurate hydrological analysis of a watershed, certain conditions need to be understood. Flow direction and flow accumulation are important watershed characteristics that need to be determined before an analysis can be made. Other important characteristics which can be gleaned from analysing the digital elevation model (DEM) of a watershed include channel networks, stream lengths and watershed boundaries. Determining flow direction and flow accumulation is usually carried out in separate steps. Flat regions are types of terrain in raster DEMs without local elevation gradients. Evaluating flow direction and flow accumulation in flat regions using DEMs is a well-known problem in watershed analysis because of the occurrence of problematic parallel flow lines. Calculations also tend to be time-consuming. We have developed an efficient and comprehensive integrated approach to assign flow directions and flow accumulation in flat regions. This approach uses values for non-flat flow accumulation and a maze algorithm with a weight value (MW method) to determine several things: a main flow line through the flat area to the local outlet, an octree tree, and first-in first-out queue structures to calculate flow accumulation. The MW method can be applied to hydrologically corrected DEMs and a single flow path can be provided to resolve all flat areas. To investigate the influence on the topological properties of the channel networks, we used this integrated algorithm to extract three sets of flow accumulation areas from existing DEMs. Using this new integrated method was faster than using the two existing methods and produced continuous channel networks without the occurrence of problematic parallel flow lines.