scholarly journals Simulating the Hydrological Processes of a Meso-Scale Watershed on the Loess Plateau, China

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 878 ◽  
Author(s):  
Manman Leng ◽  
Yang Yu ◽  
Shengping Wang ◽  
Zhiqiang Zhang

The Soil and Water Assessment Tool (SWAT) model is widely used to simulate watershed streamflow by integrating complex interactions between climate, geography, soil, vegetation, land use/land cover and other human activities. Although there have been many studies involving sensitivity analysis, uncertainty fitting, and performance evaluation of SWAT model all over the world, identifying dominant parameters and confirming actual hydrological processes still remain essential for studying the effect of climate and land use change on the hydrological regime in some water-limited regions. We used hydro-climate and spatial geographical data of a watershed with an area of 3919 km2, located on the Loess Plateau of China, to explore the suitable criterion to select parameters for running the model, and to elucidate the dominant ones that govern the hydrological processes for achieving the sound streamflow simulation. Our sensitivity analysis results showed that parameters not passing the sensitive check (p-value < 0.05) could play a significant role in hydrological simulation rather than only the parameters with p-value lower than 0.05, indicating that the common protocol is not appropriate for selecting parameters by sensitivity screening only. Superior performance of the rarely used parameter SOL_BD was likely caused by a combination of lateral and vertical movement of water in the loess soils due to the run-on infiltration process that occurred for meso-scale watershed monthly streamflow modeling, contrasting with traditionally held infiltration excessive overland flow dominated runoff generation mechanisms that prevail on the Loess Plateau. Overall, the hydrological processes of meso-scale watershed in the region could be well simulated by the model though underestimates of monthly streamflow could occur. Simulated water balance results indicated that the evapotranspiration in the region was the main component leaving the watershed, accounting for 88.9% of annual precipitation. Surface runoff contributed to 63.2% of the streamflow, followed by lateral flow (36.6%) and groundwater (0.2%). Our research highlights the importance for selecting more appropriate parameters for distributed hydrological models, which could help modelers to better comprehend the meso-scale watershed runoff generation mechanism of the Loess Plateau and provide policy makers robust tool for developing sustainable watershed management planning in water-limited regions.

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Zhixiang Lu ◽  
Songbing Zou ◽  
Zuodong Qin ◽  
Yonggang Yang ◽  
Honglang Xiao ◽  
...  

We applied an integrated approach to investigate the impacts of land use and land cover (LULC) changes on hydrology at different scales in the Loess Plateau of China. Hydrological modeling was conducted for the LULC maps from remote sensing images at two times in the Upper Fenhe River watershed using the SWAT model. The main LULC changes in this watershed from 1995 to 2010 were the transformation of farmland into forests, grassland, and built-up land. The simulation results showed that forested land contributed more than any other LULC class to water yield, but built-up land had most impact due to small initial loss and infiltration. At basin scale, a comparison of the simulated hydrological components of two LULC maps showed that there were slight increases in average annual potential evapotranspiration, actual evapotranspiration, and water yield, but soil water decreased, between the two intervals. In subbasins, obvious LULC changes did not have clear impacts on hydrology, and the impacts may be affected by precipitation conditions. By linking a hydrological model to remote sensing image analysis, our approach of quantifying the impacts of LULC changes on hydrology at different scales provide quantitative information for stakeholders in making decisions for land and water resource management.


2017 ◽  
Vol 21 (4) ◽  
pp. 1929-1945 ◽  
Author(s):  
Hong Wang ◽  
Fubao Sun ◽  
Jun Xia ◽  
Wenbin Liu

Abstract. Under the Grain for Green Project in China, vegetation recovery construction has been widely implemented on the Loess Plateau for the purpose of soil and water conservation. Now it is becoming controversial whether the recovery construction involving vegetation, particularly forest, is reducing the streamflow in the rivers of the Yellow River basin. In this study, we chose the Wei River, the largest branch of the Yellow River, with revegetated construction area as the study area. To do that, we apply the widely used Soil and Water Assessment Tool (SWAT) model for the upper and middle reaches of the Wei River basin. The SWAT model was forced with daily observed meteorological forcings (1960–2009) calibrated against daily streamflow for 1960–1969, validated for the period of 1970–1979, and used for analysis for 1980–2009. To investigate the impact of LUCC (land use and land cover change) on the streamflow, we firstly use two observed land use maps from 1980 and 2005 that are based on national land survey statistics merged with satellite observations. We found that the mean streamflow generated by using the 2005 land use map decreased in comparison with that using the 1980 one, with the same meteorological forcings. Of particular interest here is that the streamflow decreased on agricultural land but increased in forest areas. More specifically, the surface runoff, soil flow, and baseflow all decreased on agricultural land, while the soil flow and baseflow of forest areas increased. To investigate that, we then designed five scenarios: (S1) the present land use (1980) and (S2) 10 %, (S3) 20 %, (S4) 40 %, and (S5) 100 % of agricultural land that was converted into mixed forest. We found that the streamflow consistently increased with agricultural land converted into forest by about 7.4 mm per 10 %. Our modeling results suggest that forest recovery construction has a positive impact on both soil flow and baseflow by compensating for reduced surface runoff, which leads to a slight increase in the streamflow in the Wei River with the mixed landscapes on the Loess Plateau that include earth–rock mountain area.


2016 ◽  
Vol 25 (1) ◽  
pp. 054 ◽  
Author(s):  
Han Yini ◽  
Niu Jianzhi ◽  
Xin Zhongbao ◽  
Zhang Wei ◽  
Zhang Tielin ◽  
...  

Aim of study: The aim is to find a way increasing gain yield and lessen area of farmland, and then increasing vegetation cover, improving environment and alleviating soil erosion.Area of study: The Hilly-Gully region at the loess plateau of China.Material and methods: In this study, an adjusted and optimized land use pattern was developed in Luoyugou watershed in the Yellow River valley based on the gradient distribution of land use types, and its effect on water and sediment transport was simulated using the SWAT model and GIS, with remote sensing images, land use maps and hydrologic data.Main results: The results indicate: average simulated runoff and sediment for the period 1986-2000 under conditions of the three land use pattern (2011, 2008 and optimized land use) reduced by 0.002-0.013 m3/s (2.7-17.6%) and 0.66 million tons, respectively. The runoff and sediment data obtained were compared with observed data from 2008, which showed that runoff and sediment production would be reduced by 467625 m3 and 22754 tons, respectively.Research highlights: The adjustment of the land use pattern in comprehensive consideration of vegetation and geography have a positive effect on water and sediment transport which will be important for decision making and water resources management, and provides a reference for future environmental management and ecological construction in the loess plateau Hilly-Gully region. 


2021 ◽  
Author(s):  
Youcai Kang ◽  
Jianen Gao ◽  
Hui Shao ◽  
Yuanyuan Zhang

&lt;p&gt;&lt;strong&gt;Abstract: &lt;/strong&gt;Climate and land-use change are the two main driving forces that affect watershed hydrological processes. Separately assessing the impacts of climate and land use change on hydrology is important for water resource management. In this research, the SWAT (Soil and Water Assessment Tool) and statistical methods were employed to evaluate the effects of climate and land-use change on surface hydrology in the hilly-gully region of the Loess Plateau. The results showed that both the temperature and potential evapotranspiration (PET) had significant upward trends (p &lt; 0.05), while the precipitation presented a slightly downward trend in the Yanhe watershed during 1982-2012. The contribution of precipitation to streamflow is concentrated in the flooding periods (from July to September), the average contribution rate of surface runoff on stream flow accounted for 55%, of which the flooding period accounted for 40%. With the 2.17% of slope farmland transformed to the forest and grassland, the average runoff coefficient decreased from 0.36 to 0.15 during 1982-2012. The impact of land use change on soil water content is mainly happened in the upstream stream, while the dominated factor converted to climate from northwest to southeast in the Yanhe watershed. The Evapotranspiration was more sensitive to land-use change than climate variability in all sub-basins, and increased by 209% with vegetation restoration in the Yanhe watershed. Therefore, the impacts of climate variation and land use change on surface hydrological processes were heterogeneity in different geographical regions, climate is the main factor to influence the runoff, while the land use is the dominated factor to evapotranspiration. The quantitative assessment the influence of climate variability and land-use change on hydrology can provide insight into the extent of land use/cover change on regional water balance, and develop appropriate watershed management strategies on the Loess Plateau.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords: &lt;/strong&gt;climate shift, human activities, hydrological processes, SWAT, the Loess Plateau&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Funding:&lt;/strong&gt; This study was funded by the National Natural Science Foundation of China (No. 41877078, 41371276), Key research and development project of Shaanxi Province (2020ZDLSF06-03-01), National Key Research and Development Program of China (No. 2017YFC0504703) and Knowledge Innovation Program of the Chinese Academy of Sciences (No. A315021615).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;


Author(s):  
Hui Wei ◽  
Wenwu Zhao ◽  
Han Wang

Large-scale vegetation restoration greatly changed the soil erosion environment in the Loess Plateau since the implementation of the “Grain for Green Project” (GGP) in 1999. Evaluating the effects of vegetation restoration on soil erosion is significant to local soil and water conservation and vegetation construction. Taking the Ansai Watershed as the case area, this study calculated the soil erosion modulus from 2000 to 2015 under the initial and current scenarios of vegetation restoration, using the Chinese Soil Loess Equation (CSLE), based on rainfall and soil data, remote sensing images and socio-economic data. The effect of vegetation restoration on soil erosion was evaluated by comparing the average annual soil erosion modulus under two scenarios among 16 years. The results showed: (1) vegetation restoration significantly changed the local land use, characterized by the conversion of farmland to grassland, arboreal land, and shrub land. From 2000 to 2015, the area of arboreal land, shrub land, and grassland increased from 19.46 km2, 19.43 km2, and 719.49 km2 to 99.26 km2, 75.97 km2, and 1084.24 km2; while the farmland area decreased from 547.90 km2 to 34.35 km2; (2) the average annual soil erosion modulus from 2000 to 2015 under the initial and current scenarios of vegetation restoration was 114.44 t/(hm²·a) and 78.42 t/(hm²·a), respectively, with an average annual reduction of 4.81 × 106 t of soil erosion amount thanks to the vegetation restoration; (3) the dominant soil erosion intensity changed from “severe and light erosion” to “moderate and light erosion”, vegetation restoration greatly improved the soil erosion environment in the study area; (4) areas with increased erosion and decreased erosion were alternately distributed, accounting for 48% and 52% of the total land area, and mainly distributed in the northwest and southeast of the watershed, respectively. Irrational land use changes in local areas (such as the conversion of farmland and grassland into construction land, etc.) and the ineffective implementation of vegetation restoration are the main reasons leading to the existence of areas with increased erosion.


Author(s):  
Edivaldo Afonso de Oliveira Serrão ◽  
Madson Tavares Silva ◽  
Thomás Rocha Ferreira ◽  
Lorena Conceição Paiva de Ataide ◽  
Cleber Assis dos Santos ◽  
...  

2004 ◽  
Vol 79 (2) ◽  
pp. 145-170 ◽  
Author(s):  
C.H. Lu ◽  
M.K. van Ittersum ◽  
R. Rabbinge

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