土地利用变化对牤牛河流域径流的影响

土地利用变化对流域水资源配置及其循环过程有显著的影响,了解土地利用与径流的关系是流域水文学研究的重要内容。以牤牛河流域为研究区,基于SWAT分布式水文模型,利用流域DEM、土地利用、土壤、气象等数据,结合GIS和RS技术,并采用极端土地利用分析方法,对流域土地利用变化的径流响应进行定量研究与分析。结果表明:流域内1998年与2009年土地均以耕地、林地、未使用地为主,约占总面积的90%;相同的气象条件下,两期土地利用情景下年、月均径流量变化趋势一致,2009年土地利用情景下的年、月径流量较1998年略小,年均径流量减少605.5万m3;7,8月份月径流模拟减少量明显;土地植被覆盖度增大径流量减小,反之则增大;在极端土地利用情景下,径流量将发生剧烈变化。因此,在不考虑研究期间内气候变化等因素的条件下,土地利用变化是影响流域径流变化的主要因素。     

Rainfall-Runoff Modeling: Comparison of Two Approaches with Different Data Requirements

Among several hydrological models developed over the years, the most widely used technique for estimating direct runoff depth from storm rainfall i.e., the United States Department of Agriculture (USDA) Soil Conservation Service’s (SCS) Curve Number (CN) method was adopted in the present study. In addition, the Muskingum method, which continues to be popular for routing of runoff in river network, was used in the developed model to route surface runoffs from different subbasin outlet points up to the outlet point of the catchment. SCS CN method in combination with Muskingum routing technique, however, required a detailed knowledge of several important properties of the watershed, namely, soil type, land use, antecedent soil water conditions, and channel information, which may not be readily available. Due to this complexity of semi-distributed conceptual approach (SCS CN method) and non-linearity involved in rainfall-runoff modeling, researchers also attempted another less data requiring approach for runoff prediction, i.e., the neural network approach, which is inherently suited to problems that are mathematically difficult to describe. The purpose of this study was to compare the rainfall-runoff modeling performance of semi-distributed conceptual SCS CN method (in combination with Muskingum routing technique) with that of empirical ANN technique. The models were coded in C language and to make them user friendly, a Graphical User Interface (GUI) was also developed in Visual Basic 6.0. The developed models were tested for Kangsabati catchment, situated in the western part of West Bengal, India. Monsoon data of 1996 to 1999 were used for calibration of the models whereas they were validated for another four years (1987, 1989, 1990, and 1993) monsoon data. Modeling efficiency (ME) and coefficient of residual mass (CRM) were used as performance indicators. Results indicated that for Kangsabati catchment, the empirical runoff prediction approach (ANN technique), in spite of requiring much less data, predicted daily runoff values more accurately than semi-distributed conceptual runoff prediction approach (SCS CN method).     

Hydrologic modelling for runoff determination

The quantitative assessment of runoff from a catchment is necessitated when a structure in the vicinity of a watercourse has to be designed. In the present study the USDA Soil Conservation Service runoff curve numbers, modified for Indian conditions, are established for the Kaliaghai river basin from a digitized land‐use or land‐cover map derived from IRS‐IA LISS‐II data. The software ‘HYDMOD’ was developed to translate the curve number into volume of runoff. The linear regression model was developed to correlate the observed and estimated runoff. Average percentage deviation between the observed and estimated runoff was found to be in the order of 5.9.     

GIS Based Estimation of Sediment Discharge and Areas of Soil Erosion and Deposition for the Torrential Lukovska River Catchment in Serbia

In the present study the SHETRAN river basin modelling system was used in conjunction with Geographic Information System (GIS) to estimate potential erosion and deposition rates within the catchment and the concentrations of sediment in a flow at the catchment outlet on the example of the 114.31 km² mountainous torrential Lukovska River catchment in Serbia. The streams in the Lukovska River catchment are short, steep and often produce hazardous torrential floods as a consequence of strong rainfall of short duration. The soil erosion and sediment discharge were analysed in view of the catchment response to physical characteristics of the catchment. Considering that the most of total annual sediment discharge in watersheds of torrential character is achieved during storm events, the SHETRAN modelling system was calibrated on the example of a storm event in 1986 and validated for three other storm events in 1974, 1976 and 1979. The simulated results of discharges and sediment concentrations at the catchment outlet for both calibration and validation events were compared with the observed data and found to be reasonable. The changes of erosion and deposition rates within the catchment and in the course of time were estimated for the calibration event in 1986. The simulated erosion rates were within the range of 1 to 10.5 t/ha and corresponded to the observed rates of erosion in Europe during extreme rain events. The presented methodology is useful in identifying the erosion vulnerable regions in a catchment where erosion control measures should be implemented.     

Developing an independent, generic, phosphorus modelling component for use with grid-oriented, physically based distributed catchment models.

Grid-oriented, physically based catchment models calculate fields of various hydrological variables relevant to phosphorus detachment and transport. These include (i) for surface transport: overland flow depth and flow in the coordinate directions, sediment load, and sediment concentration and (ii) for subsurface transport: soil moisture and hydraulic head at various depths in the soil. These variables can be considered as decoupled from any chemical phosphorus model since phosphorus concentrations, either as dissolved or particulate, do not influence the model calculations of the hydrological fields. Thus the phosphorus concentration calculations can be carried out independently from and after the hydrological calculations. This makes it possible to produce a separate phosphorus modelling component which takes as input the hydrological fields produced by the catchment model and which calculates, at each simulation time step, the phosphorus concentrations in the flows. This paper summarises the equations and structure of such a Grid Oriented Phosphorus Component (GOPC) developed by the authors for simulating phosphorus concentrations and loads using the outputs of a fully distributed physical based hydrological model. The GOPC performance is illustrated by an example of a simplified hypothetical catchment subjected to some ideal conditions.     

分布式水文概念性模型及应用

在遥感与GIS支持下,建立地理空间信息库,提取了流域土地利用、土壤类型和植被类型等地理信息及相应的水空间参数,采用已有的水概念性模型,建立了一个分布式水概念性模型．模型结构简单,所需参数较少,易于率定,可操作性强．实例应用表明,该模型对雁栖河流域径流量的模拟是有效的,可用于评估流域水资源量、气候变化以及土地利用变化对水资源的影响．     

Modeling of Surface Runoff in Xitiaoxi Catchment,China

Xitiaoxi catchment is one of the most important catchments in the Taihu basin in China. Due to its significant contribution of surface runoff and associated nutrients input to Lake Taihu, understanding of the processes of surface runoff in this catchment is, therefore, of primary importance in quantifying water and nutrient balances for Lake Taihu. The generation of surface runoff in the catchment is mainly controlled by rainfall and land cover, so the variety of surface runoff in Xitiaoxi catchment is seasonal. Moreover, the annual change of surface runoff is distinct. Because of the diversity of land use and variety of hydrological characteristics, numerical simulation of the generation of surface runoff over this catchment is not straightforward. In this paper, attempts were made in applying the Large Scale Catchment Model (LASCAM) to Xitiaoxi catchment. The Xitiaoxi catchment is divided into 47 subcatchments connected via a river network based on topology. The model was first run in an optimization mode to calibrate the parameters against the observed runoff for the period of 1968–1977, and then was run in a prediction mode to try to reproduce the runoff for the next 10 years from 1978 to 1987. The model indicates that saturation excess runoff is probably the dominant process for the catchment. The modeling results indicate that water storage in shallow soils near the stream has a high correlation with daily rainfall, while the water storage changes in deep aquifers demonstrate an annual change trend, showing a rising level for wet seasons and a declining level for dry seasons. The success in modeling surface runoff leads to confidence in modeling nutrients transport as the next step of modeling work.     

Flood Modeling for Complex Terrain Using GIS and Remote Sensed Information

A spatially distributed hydrological model WetSpa (Water and Energy Transfer between Soil, Plants and Atmosphere) working on an hourly time scale is presented in this paper. The model combines elevation, soil and land use data, and predicts flood hydrograph and the spatial distribution of hydrological characteristics in a watershed. The model is tested on a small catchment in Belgium for which topography and soil data are available in GIS form, while the land use and soil cover is obtained from remote sensed images. The resulting calculated discharges compare favorably with the field measurements. Next a 102-year series of measured hourly precipitation data is processed with the model and the resulting hydrographs are analyzed statistically to determine the characteristics of extreme floods. Finally, the simulated extreme peak discharges are compared to the results calculated with design storms. Comparison of the two methods shows that the model is capable to predict both normal and extreme floods. Since the model accounts for spatially distributed hydrological and geophysical characteristics of the catchment, it is suitable for simulating hydrological processes in a complex terrain and for predicting the influence of changes in land use on the hydrological behavior of a river basin.     

An Empirical Water Budget Model As a Tool to Identify the Impact of Land-use Change in Stream Flow in Southeastern Australia

In western Victoria, Australia the water table and lake level in the Glenelg-Hopkins catchment have been declining for the last 15 years, and this is attributed to either the low rainfall over this time and/or a substantial change in land use. Stream flow modelling was carried out using monthly empirical water balance model (modified tanh function together with double mass curve analysis), on 37 stream gauges to assess whether the impact of land use change could be detected by a change in the magnitude of the resulting runoff. The empirical hydrological model was able to distinguish impact of land use change on stream flow from the climatic variables. There were substantial decreases in stream flow in the 1970s–1980s, probably related to increasing livestock densities in the region. Furthermore, the methodology can be a powerful tool to monitor and evaluate the possible impacts of future land use changes. It can be concluded that the use of such empirical hydrological modelling greatly improves the ability to analyse the impact of land use on catchment runoff. The model is a practical tool that can be readily used for identifying and quantifying the effect of landuse changes on catchment for water resource decision-making, which could be hardly possible using the time consuming, data hungry and expensive physical process models available.     

基于SWAT和GIS的洱海流域土地利用变化对径流影响的研究

利用DEM、土地利用、土壤、气象等时空数据并结合GIS和RS技术,建立洱海流域SWAT模型,分析了2000年和2010年不同土地利用情景对径流的影响,其结果为洱海流域土地利用变化引起径流的变化率为2.46%。以《云南省土地利用总体规划大纲(2006—2020)》为依据,结合洱海流域土地利用分布的实际情况,设置3种土地利用情景,研究不同土地利用情景对径流的影响。结果表明情景1中,66.06 km²的耕地转林地和89.16 km²的耕地转草地,模拟的年均径流值增加75.73 mm;情景2中,100.13 km²的裸地和105.74 km²的草地转为耕地,年均径流增加39.89 mm;情景3中,138.72 km²的草地和292.86 km²林地转耕地,年均径流减少20.36 mm。模拟表明在坡度15°以上,洱海流域森林和草地面积的增加将会增加径流量;在坡度15°以下,耕地的增加会一定程度上减少径流量。研究成果为洱海流域水资源空间合理调配提供参考依据。     

Improvement to the Thornthwaite Method to Study the Runoff at a Basin Scale Using Temporal Remote Sensing Data

Most of the popular hydrological models are intensive data driven hence, it has become a constraint in computing runoff of river basins where the meteorological data availability is scant. Studying environmental impact assessment on runoff has also become complex in many basins due to non-availability of sufficient historic meteorological data. Directly or indirectly, major components of hydrological cycle such as evapotranspiration and soil moisture are dependent on land use pattern at basin scale. Keeping in view of this, in this paper, an attempt was made to propose modification to simple monthly water balance model by integrating potential evapotranspiration with land use coefficients that were derived from the temporal satellite remote sensing data to compute runoff at basin scale. Godavari Basin, India was selected as study basin to demonstrate the approach. Monthly land use coefficients of all land use classes were computed during the calibration process of the model by matching the computed runoff with field runoff. Runoff during the last 18 years (1990–91 to 2007–08) was computed using the developed methodology. Four years datasets were used for model calibration and the rest of the data for model validation. Spatial annual groundwater flux, reservoir flux and domestic water consumption grids were computed using the field data and integrated with the model in computing runoff. From the Nash-Sutcliffe efficiency coefficient, it is found that computed runoff is very well matching the field runoff. The demonstrated approach is found to be more accurate and simple in computing runoff at basin scale in absence of high intensity meteorological data.     

巢湖流域土地利用变化对雨洪调蓄能力的影响

为探究土地利用结构变化对雨洪调蓄能力的影响,以1980—2020年巢湖流域的土地利用数据和土壤数据为基础,采用GIS和SCS模型相结合的方法,分析了不同时期不同降雨尺度下巢湖流域径流产生及分布情况。结果表明：1980—2020年巢湖流域土地利用变化主要表现为建设用地的增加及耕地和林地的减少;流域土地利用综合指数持续增长,其中高强度土地利用区面积从127 km²增长到了1 624 km²。1980—2020年渗透性差的地区从1 706.0 km²增加到了2 398.1 km²,以城市区域扩张为主。2020年相较于1980年,在不同土地利用条件下,相同降雨量时径流量明显增大,且主要在巢湖流域的合肥地区,而在增加降雨量时,径流量的增加幅度逐渐减小,在不同降雨量条件下(日降雨量为50、100、250 mm)径流量分别增大了6.11%、2.61%和0.96%。因此可以得出土地利用变化是导致径流量变化的主要因素,降雨量是次要因素。研究结果可为巢湖流域城市规划及城市雨洪风险管理提供参考。     

黄土高原流域土地利用变化的水土流失效应

本文以黄土高原中部的油河流域为例,利用3个不同时期的遥感影像分析了1977年以来的讷河流域的土地利用变化特征,在此基础上,选择年径流深度、年侵蚀模数、汛期径流深度、汛期侵蚀模数和枯季径流深度为水土流失过程参数,通过基于流域降水与水土流失过程各参数的统计回归模拟分析,区分出了降水和土地利用等地表属性变化分别导致的流域水土流失变化过程.研究结果认为:1980年以来,流域水土流失明显趋缓,以10年为尺度得出的平均值,径流深度减少了32.75mm,侵蚀模数减少了778t/km2.水土流失的变化主要是由地表属性变化引起的,降水量变化的贡献很小.耕地面积变化和地表属性变化引起的水土流失变化具有显著的相关性,坡耕地改梯田的农田水利建设可能是导致水土流失变化的主要原因.     

Quantification of soil erosion and sediment yield for ungauged catchment using the RUSLE model: Case study for Lake Basaka catchment in Ethiopia

Soil erosion is a monumental land degradation problem in many parts of the world, threatening the well‐being of humans and ecosystems. The Lake Basaka catchment is heavily affected by serious land degradation problems related to land use–land cover changes (LULC), population dynamics and settlement, introduction of large‐scale irrigation schemes, etc. Accordingly, the objective of the present study was to quantify the magnitude of soil lost from the Lake Basaka catchment and the sediment subsequently delivered to the lake on the basis of the limited available dataset in a distributed manner using the RUSLE model in a GIS environment. The results indicated about 36 million m³ of soil were lost from the catchment between 1973 and 2007. Soil erosion and sedimentation in the lake catchment continue to increase from time to time, being attributed to the significant LULC occurring in the catchment. About 23 cm of the economically productive top soil in the catchment was lost during the study period (1960–2015), which translates into a significant degradation of the catchment (e.g. further reduction of infiltration capacity, thereby accelerating run‐off and erosion rates). Similarly, about a 1.3 m deep sediment layer was deposited in the lake during the same period. The computed sediment yield indicates about 14% of the lake incremental volume and depth in recent periods (post‐2000s) is attributable to sedimentation. Certain coincidental changes are also occurring in the catchment, including organic matter declines, soil nutrient depletion and soil depth decrement, which may lead to decreased production and productivity and associated ecosystem imbalances. The present study identified the potential areas that contribute significantly to erosion and sedimentation, thereby providing guidance regarding where land use/cover practices must be implemented to limit/reduce, if not avoid, the impacts of erosion and subsequent sedimentation in Lake Basaka.     

Development of a distributed hydrological model based on urban databanks--production processes of URBS.

The objective of this study is to present a distributed hydrological model especially dedicated to urban catchments, and able to represent hydrological processes usually neglected in urban modelling, such as evapotranspiration, infiltration in roads, or direct infiltration of soil water in sewers. This model, called URBS (as Urban Runoff Branching Structure) is distributed considering the spatial variability of land use which is well known thanks to urban databanks managed by GIS. The production function is detailed at each cadastral parcel scale, and the runoff produced is routed by a simple transfer function. The estimation of the input parameters of the model is mostly based on physical considerations, and the model is applied on a suburban catchment in Nantes (France) in order to evaluate the interest of the distribution of the hydrological variables.     

利用地理信息系统进行流域径流量计算的方法研究

流域径流模拟通常要涉及流域地形、土壤类型、土地利用等地理参数,对于小流域可以假定其地理参数变化不大,全流域采用均一参数,而对于大流域采用均一参数则不能准确反映流域的地理特性。本文以渭河流域陕西片为计算实例,应用地理信息系统(G IS)分析流域地理参数,计算流域径流量。     

Estimation of Soil Erosion and Sediment Yield Using GIS at Catchment Scale

A GIS-based method has been applied for the determination of soil erosion and sediment yield in a small watershed in Mun River basin, Thailand. The method involves spatial disintegration of the catchment into homogenous grid cells to capture the catchment heterogeneity. The gross soil erosion in each cell was calculated using Universal Soil Loss Equation (USLE) by carefully determining its various parameters. The concept of sediment delivery ratio is used to route surface erosion from each of the discritized cells to the catchment outlet. The process of sediment delivery from grid cells to the catchment outlet is represented by the topographical characteristics of the cells. The effect of DEM resolution on sediment yield is analyzed using two different resolutions of DEM. The spatial discretization of the catchment and derivation of the physical parameters related to erosion in the cell are performed through GIS techniques.     

WetSpa Model Application for Assessing Reforestation Impacts on Floods in Margecany–Hornad Watershed,Slovakia

The spatially distributed hydrologic model WetSpa working on a daily or hourly time scale combines elevation, soil and landuse data within GIS, to predict flood hydrographs and spatial distribution of hydrologic characteristics in a watershed. The model is applied to the Margecany–Hornad river basin (1,131 km²) located in Slovakia. Daily hydrometeorological data from 1991 to 2000, including precipitation data from nine stations, temperature data from four stations and evaporation data measured at one station are used as input to the model. Three base maps, i.e., DEM, landuse and soil types are prepared in GIS form, using 100×100 m cell size. Results of the simulations show good agreement between calculated and measured hydrographs at the outlet of the basin. The model predicts the daily/hourly hydrographs with good accuracy, between 75–80% according to the Nash–Sutcliff criteria. For assessing the impact of forests on floods, the calibrated model is applied for a reforestation scenario using the hourly data of the summer of 2001. The scenario considers a 50% increase of forest areas. The model results show that the reforestation scenario decreases the peak discharge by 12%. Investigation of peak discharges from the whole simulation period, shows that the scenario results are reduced by 18% on average. Also, the time to peak of the simulated hydrograph of the reforestation scenario is 14 h longer than for the present landuse. The results show that the effect of land cover on flood is strongly related to storm characteristics and antecedent soil moisture.