Impact assessment of land cover changes on the runoff changes on the extreme flood events in the Kelantan River basin

In the current years, changing the land cover/land use had serious hydrological impacts affecting the flood events in the Kelantan River basin. The flood events at the east coast of the peninsular Malaysia got highly affected in the recent decades due to several factors like urbanisation, rapid changes in the utilisation of land and lack of meteorological (i.e. change in climate) and developmental monitoring and planning. The Kelantan River basin has been highly influenced due to a rapid change in land use during 1984 to 2013, which occurred in the form of transformation of agricultural area and deforestation (logging activities). In order to evaluate the influence of the modifications in land cover on the flood events, two hydrological regional models of rainfall-induced runoff event, the Hydrologic Engineering Center (HEC)-Hydrologic Modeling System (HMS) model and improved transient rainfall infiltration and grid-based regional model (Improved TRIGRS), were employed in this study. The responses of land cover changes on the peak flow and runoff volume were investigated using 10 days of hourly rainfall events from 20 December to the end of December 2014 at the study area. The usage of two hydrological models defined that the changes in land use/land cover caused momentous changes in hydrological response towards water flow. The outcomes also revealed that the increase of severe water flow at the study area is a function of urbanisation and deforestation, particularly in the conversion of the forest area to the less canopy coverage, for example, oil palm, mixed agriculture and rubber. The monsoon season floods and runoff escalate in the cleared land or low-density vegetation area, while the normal flow gets the contribution from interflow generated from secondary jungle and forested areas.     

喀斯特流域分布式水文模型及植被生态水文效应

根据喀斯特流域多孔介质与裂隙水流特征,建立了达西流、裂隙渗流与槽蓄汇流演算相结合的混合汇流演算模式,实现了对分布式水文-植被-土壤模型(DHSVM)的改进。利用贵州普定喀斯特生态水文试验站陈旗小流域观测资料,对模型计算的流量过程及植被截流、蒸散发及土壤含水率时空分布进行验证。结果表明,模型能较好地模拟喀斯特流域陡涨、陡落的流量过程。同时,模型能模拟出土壤含水率、实际蒸散发与降雨、下垫面岩溶裂隙、植被覆盖的响应关系,对分析中国南方喀斯特地区下垫面变化条件下的生态水文效应具有重要意义。     

Uncertainty analysis of HEC-HMS model using the GLUE method for flash flood forecasting of Mekerra watershed,Algeria

In this paper, the lumped quasi-distributed hydrological model HEC HMS is used to simulate the rainfall–runoff process of the Mekerra watershed, located in the northwest of Algeria. The model parameters’ uncertainty and the predictive intervals were evaluated with the generalized likelihood uncertainty estimation (GLUE) approach. According to the results, good simulations were obtained with different values of variables for many sets of parameters generated randomly by the Monte Carlo procedure, which is known as Equifinality. After the analysis, only the hydraulic conductivity at saturation parameter appears well defined, taking values within a limited range. In addition, results indicated that combinations of likelihood measures associated with multiple and different periods of observations reduce a posterior uncertainty of estimated parameters and predictive intervals in some degree. Overall, the GLUE analysis showed that there is a significant uncertainty associated with hydrological modelling of watershed Mekerra, to a great extent due to multiple sources of errors.     

Hydrology models approach to estimation of the groundwater recharge: case study in the Bulgarian Danube watershed

The groundwater (GW) makes an important part of a region runoff. GW bodies playing the role of accumulating reservoirs regulate the GW discharge enabling the river flow to have more uniform long-term distribution. Along with other important advantages, the GW offers the users stable water abstraction rate independent from the recharge rate. The GW recharge quantification belongs to the uneasy tasks in the water resource management. Applying the conventional methods needs multiyear observation records of the variation of the groundwater body (GWB) characteristics. The employment of hydrology models avoids that necessity but requires great amount of data related to the soil hydraulic properties, the land topography and cover of the GWB watershed and long-term records of the climatic effects. The paper presents an introduction of the mathematical model CLM3 into the GW recharge estimation problem. It is a complex and advanced model with adequate interpretation of the water-related processes in the soil and on the land surface under atmospheric effects. The input is available from NCEP/NCAR reanalysis atmosphere data and the International Geosphere-Biosphere Program (IGBP) data base. The model is applied to GW recharge assessment of the Bulgarian Danube district for the year 2013. The obtained monthly and yearly total district values and the areal distribution of the infiltration intensity are matched to the existing field observation-based estimates. The study shows that the CLM3 model approach leads to encouraging results. The method comes very useful with GWB lacking regime observation data as well as for GW recharge prognostic assessments under climatic scenarios.     

水文模型系统在峨嵋河流域洪水模拟中的应用

研究目的是采用水文模型系统(HMS)模拟峨嵋河流域暴雨水文过程,并为长江上游地区气候和水文响应研究提供可靠的信息。HMS是一种分布式水文模型可用于研究各种气候因子和地表覆盖变化而引起的水文过程响应,该系统(HMS)利用气象、土壤类型、土地利用和地表覆盖、数字高程(DEM)和降雨径流等资料,研究气候、陆面、地表水和地下水的相互作用机理。在本次研究中,采用SCS Curve Number(CN)和Green-Ampt(GA)方法来计算径流过程,用GIS来数字化DEM、土壤、土地利用和陆地覆盖数据。通过用不同时间间隔的降雨和不同计算方法的水力参数模拟水文过程,来检验降雨的时间尺度效应和水力参数的空间变异性对水文过程的影响。结果表明,HMS对峨嵋河流域暴雨洪水的模拟及预测具有较好的适用性。     

Evaluation of sediment yield and soil loss by the MPSIAC model using GIS at Golestan watershed, northeast of Iran

Watershed degradation due to soil erosion and sedimentation is considered to be one of the major environmental problems in Iran. In order to address the critical conditions of watershed degradation in arid and semiarid regions, a study based on the Modified Pacific Southwest Inter-Agency Committee (MPSIAC) model was carried out at Golestan watershed, northeast of Iran. The model information layers comprising nine effective factors in erosion and sedimentation at the watershed site were obtained by digitalization and spatial interpolation of the basic information data in a GIS program. These factors are geology, soil, climate, runoff, topography, land cover, land use, channel, and upland erosion. The source data for the model were obtained from available records on rainfall and river discharge and sediment, topography, land use, geology, and soil maps as well as field surveys and laboratory analysis. The results of the MPSIAC model indicated that 60.75 % (194.4 km²) and 54.97 % (175.9 km²) of the total watershed area were classified in the heavy sedimentation and erosion classes, and the total basin sediment yield and erosion were calculated as 4,171.1 and 17,813.4 m³ km^?2 year^?1, respectively. In the sensitivity analysis, it was found that the most sensitive parameters of the model in order of importance were topography (slope), land cover and use, runoff, and channel erosion (R ²?=?0.92–0.94), while geology, climate (rainfall), soil, and upland erosion factors were found to have moderate effect to the model output (R ²?=?0.74–0.59).     

Land use and land cover change and implication to watershed degradation by using GIS and remote sensing in the Koga watershed,North Western Ethiopia

Information on use/land cover change is important for planners and decision makers to implement sustainable use and management of resources. This study was intended to assess the land use land cover (LULC) change in the Koga watershed. The MSS of 1973, TM images of 1986, 1995 and 2011 were used together with survey and demographic data to detect the drivers of land cover changes. The result revealed that a remarkable LULC change occurred in the study area for the past thirty eight years. The area of cultivated and settlement has increased by 7054.6 ha, while, grass and bush lands decreased by 4846.5 and 3376 ha respectively. Wetland also declined from 580.2 ha to 68.3 ha. The growing demand for cultivable land and fuel wood were the major causes to the deterioration of grass and bush lands. Hence, the appropriate land use policy should be employed to sustain available resource in the watershed.     

RETRACTED ARTICLE: Assessment of soil erosion using RUSLE and GIS: a case study of the Maotiao River watershed,Guizhou Province,China

Due to the existence of fragile karst geo-ecological environments, such as environments with extremely poor soil cover, low soil-forming velocity, and fragmentized terrain and physiognomy, as well as inappropriate and intensive land use, soil erosion is a serious problem in Guizhou Province, which is located in the centre of the karst areas of southwestern China; evaluation of soil loss and spatial distribution for conservation planning is urgently needed. This study integrated the revised universal soil loss equation (RUSLE) with a GIS to assess soil loss and identify risk erosion areas in the Maotiao River watershed of Guizhou. Current land use/cover and management practices were evaluated to determine their effects on average annual soil loss and future soil conservation practices were discussed. Data used to generate the RUSLE factors included a Landsat Thematic Mapper image (land cover), digitized topographic and soil maps, and precipitation data. The results of the study compare well with the other studies and local data, and provide useful information for decision makers and planners to take appropriate land management measures in the area. It thus indicates the RUSLE–GIS model is a useful tool for evaluating and mapping soil erosion quantitatively and spatially at a larger watershed scale in Guizhou.     

天津北三河地区垂向耦合产流模型及应用

针对平原地区下垫面多样性的特点,将天津北三河地区下垫面划分为水面、农业用地和城镇建设用地3类,分别采用不同的产流模型。由于北三河地区农业用地主要为旱地,普遍存在犁底层;因此将非饱和带分为耕作层、犁底层和基础层3部分,分别采用蓄满产流、层间超渗产流和蓄满产流耦合产流模式,并考虑犁底层中大孔隙的存在对产流的影响。用北三河第9产流分区1966、1971、1974、1975、1976年资料建立产流模型,用1977年和1982年资料进行检验,合格率达85.7%。应用结果表明,该模型符合实际情况,可以反映北三河地区的水文特点,为平原地区水文分析提供参考。     

Watershed urbanization and changing flood behavior across the Los Angeles metropolitan region

This article examines the effects of watershed urbanization on stream flood behavior in the Los Angeles metropolitan region. Stream gauge data, spatially distributed rainfall data, land use/land cover, and census population data were used to quantify change in flood behavior and urbanization in multiple watersheds. Increase in flood discharge started at the very early stage of the urbanization when the population density was relatively low but the rate of increase of flood discharge varied across watersheds depending on the distribution of the imperviousness surface and flood mitigation practices. This spatial variability in rainfall–runoff indices and the increasing flood risk across the metropolitan region has posed a challenge to the conventional flood emergency management, which usually responds to flood damages rather than being concerned with the broader issues of land use, land cover, and planning. This study pointed out that alternative land use planning and flood management practices could be mitigating the urban flood implemented hazard.     

Application of the modified universal soil loss equation (MUSLE) in prediction of sediment yield (Case study: Kengir Watershed, Iran)

Modified Universal Soil Loss Equation (MUSLE) application study is undertaken in order to estimate the sediment yield of the Kengir watershed in Iyvan City, Ilam Province, Iran. The runoff factor of MUSLE is computed using the measured values of runoff and peak rate of runoff at outlet of the watershed. Topographic factor (LS) and crop management factor(C) are determined using geographic information system (GIS) and field-based survey of land use/land cover. The conservation practice factor (P) is obtained from the literature. Sediment yield at the outlet of the study watershed is simulated for six storm events spread over the year 2000 and validated with the measured values. The high coefficient of determination value (0.99) indicates that MUSLE model sediment yield predictions are satisfactory for practical purposes.     

Application of remotely sensed imagery to watershed analysis a case study of Lake Karoun, Egypt

Delineation of Lake Karoun watershed in Egypt was carried out and various watershed parameters and environmental characteristics were extracted using geographic information system and remote sensing. Environmental characteristics including normalized vegetation index (NDVI), moisture index, land surface temperature, and land use classes were obtained from high spatial resolution images (Landsat TM). Moreover, hydrological parameters, drainage flow directions, drainage networks, and catchments from digital elevation model have been delineated using the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) satellite images. As a result, the lake's watershed characteristics including the environmental and hydrological factors for each watershed zone were presented and analyzed. The information generated would be of immense help in hydrological modeling of watershed for prediction of runoff and sediment yield, thereby providing necessary inputs for developing suitable developmental management plans with sound scientific basis.     

Effects of land use change on flood characteristics in mountainous area of Daqinghe watershed, China

Land use has changed in the Daqinghe watershed during 1956–2005, and it has influenced the flood peak and volume. In order to reveal the effects of land use change on flood characteristics in Daqinghe watershed, we selected 2 sub-watersheds and used remote-sensed land use data of 1980 and 1996 to analyze changes in land use and also selected several combinations of similar rainfall events and the corresponding flood events to show how changes in land use affect floods. The forest and urban area increased and other types decreased, and flood peaks and volumes tended to decrease under similar rainfall events. To quantify the extent of change in land use affecting floods, a hydrological model incorporating the land use was established. The model combines infiltration excess and saturation excess runoff generation mechanism in each type of land use, and the simulation results agreed well with the measured flood processes in the two selected watersheds. Several floods of different return intervals were selected to be modeled under the 1980 and 1996 land use conditions. The results show that both flood peak and volume decreased under the 1996 land use condition in comparison with the 1980 land use condition in the two watersheds. Most of the flood peaks decreased <5 %, but the volume decreased to a greater extent. This result can be helpful in modifying design flood.     

基于Erlang分布蓄水容量曲线的流域产流模型

蓄水容量曲线是反映流域缺水量空间分布不均匀性的特征曲线,对流域产流计算有直接影响。通过对多个典型流域蓄水容量空间分布的分析,发现Erlang分布能更好地拟合流域的蓄水容量曲线,进一步基于Erlang分布进行流域产流的推导,提出了基于Erlang分布蓄水容量曲线的流域产流模型。应用结果表明,基于Erlang分布的流域产流模型,增加了模型的适应性,模拟结果更接近流域实际的产流过程,比新安江模型能取得更高的模拟精度。此外,该产流模型的参数可由流域地形和土壤类型数据估算,为无资料地区的产流计算提供了一种可行的途径。     

Modeling the effects of controlled drainage at a watershed scale using SWATDRAIN

The recently developed SWATDRAIN model was employed to assess the impact of controlled drainage on the water table dynamics, subsurface drainage, and surface runoff in an agricultural watershed in Ontario, Canada. Controlled drainage was defined with a depth of 1.0 m to restrict flow at the drain outlet to maintain the water table at 0.5 m below the surface level during the winter (November–April) and at 0.6 m during the summer (June–August) months. The effects of the absence, or implementation, of drainage water management were predicted for the 3-year period of 1991–1993. Implementing controlled drainage resulted in a 16 % reduction in the mean annual drain flow, while increasing surface runoff by as much as 71 %. This indicates that overall watershed hydrology could be significantly impacted by the implementation of controlled drainage. This research demonstrates the SWATDRAIN model’s ability to predict the controlled drainage in small agricultural watersheds.     

Effects of land-use change on nutrient discharges from the Patuxent River watershed

We developed an empirical model integrating nonpoint source (NPS) runoff, point sources (PS), and reservoir management to predict watershed discharges of water, sediment, organic carbon, silicate, nitrogen, and phosphorus to the Patuxent River in Maryland. We estimated NPS discharges with linear models fit to measurements of weekly flow and 10 material concentrations from 22 study watersheds. The independent variables were the proportions of cropland and developed land, physiographic province (Coastal Plain or Piedmont), and time (week). All but one of the NPS models explained between 62% and 83% of the variability among concentration or flow measurements. Geographic factors (land cover and physiographic province) accounted for the explained variability in largely dissolved material concentrations (nitrate [NO₃], silicate [Si], and total nitrogen [TN]), but the explained variability in flow and particulates (sediment and forms of phosphorus) was more strongly related to temporal variability or its interactions with land cover and province. Average concentrations of all materials increased with cropland proportion and also with developed land (except Si), but changes in cropland produced larger concentration shifts than equivalent changes in developed land proportion. Among land cover transitions, conversions between cropland and forest-grassland cause the greatest changes in material discharges, cropland and developed land conversions are intermediate, and developed land and forest-grassland conversions have the weakest effects. Changing land cover has stronger effects on NO₃ and TN in the Piedmont than in the coastal Plain, but for all other materials, the effects of land-use change are greater in the Coastal Plain. We predicted the changes in nutrient load to the estuary under several alternate land cover configurations, including a state planning scenario that extrapolates current patterns of population growth and land development to the year 2020. In that scenario, declines in NPS discharges from reducing cropland are balanced by NPS discharge increases from developing an area almost six times larger than the lost cropland. When PS discharges are included, there are net increases in total water, total phosphorus, and TN discharges.     

Assessing impact of urban impervious surface on watershed hydrology using distributed object-oriented simulation and spatial regression

In this study, we investigated the relationship between watershed characteristics and hydrology using high spatial resolution impervious surface area (ISA), hydrologic simulations and spatial regression. We selected 20 watersheds at HUC 12 level with different degrees of urbanization and performed hydrologic simulation using a distributed object-oriented rainfall and runoff simulation model. We extracted the discharge per area and ratio of runoff to base flow from simulation results and used them as indicators of hydrology pattern. We derived percentage of ISA, distance from ISA to streams, and stream density as the watershed characteristics to evaluate the relationship with hydrology pattern in watersheds using ordinary least square, spatial error and spatial lag regression models. The comparison indicates that spatial lag regression model can achieve better performance for the evaluation of relationship between ratio of runoff to base flow and watershed characteristics, and that three models provide similar performance for the evaluation of relationship between discharge per area and watershed characteristics. The results from regression analyses demonstrate that ISA plays an important role in watershed hydrology. Ignorance of spatial dependence in analyses will likely cause inaccurate evaluation for relationship between ISA and watershed hydrology. The hydrologic model, regression methods and relationships between watershed characteristics and hydrology pattern provide important tools and information for decision makers to evaluate the effect of different scenarios in land management.     

黄河数字流域模型的建立和应用

黄河数字流域模型是“数字黄河”的重要组成部分,在数字流域模型框架下,以坡面为基本单元,建立了包括植被截留、融雪、地表蓄滞、表层土蓄滞、中层土蓄滞和深层土蓄滞共6层的产流模型.模型在垂向上考虑3层出流:地表超渗产流、表层土侧向渗流和中层土侧向渗流,既反映当前的降水过程,又体现前期降水过程和土壤前期含水量的影响,比较适合黄河流域的产流特点.在坡面产流的基础上,还给出了坡面单元侵蚀产沙公式,用于建立流域产沙数学模型.应用建立的模型,给出了3个计算实例:黄河全流域水量计算、小花区间汛期洪水模拟和多沙粗沙区产沙计算.实践表明:建立的模型基本具备了在黄河全流域进行降雨-径流模拟、侵蚀产沙计算的功能,辅以降雨预报模块则可进行洪水预报.     

Groundwater vulnerability mapping for a sub-catchment of the Rio La Venta watershed,Chiapas, Mexico

Karst systems are particularly vulnerable to overexploitation and pollution due to their high hydraulic conductivity and points of rapid infiltration that allow quick influx of runoff and pollutants into the aquifer. The sustainability of non-contaminated groundwater in these systems is imperative for both humans and groundwater-dependent ecosystems. An important practice in managing groundwater sustainability involves assessing aquifer vulnerability. This study created the first groundwater vulnerability map (GVM) for a sub-catchment of the Rio La Venta watershed in Chiapas, Mexico, using an adaptation of the hazard–pathway–target method. This project also conducted the first tracer study in the Rio la Venta watershed to establish connectivity between the catchment and the Rio La Venta Canyon. Finally, this study evaluated the results of the GVM through a sensitivity analysis. Results of the GVM clearly demarcate areas of very high, high, moderate, and low vulnerability within the study area most of which being classified as low vulnerability. The zones of high vulnerability were successfully validated through two dye tracer tests that measured rapid groundwater flow velocities. With the limited resources available to land managers in this area, a problem common in many developing countries, tools that quickly and inexpensively highlight areas that require special protection to help maintain or improve water quality in their watersheds have great utility. Conveying this information to land managers and policymakers can lead to potential changes in current land use practices and allow for the reallocation of resources in support of reducing future negative human–landscape interactions.     

Simulation of surface runoff in theWujiang River watershed based on GIS

Surface runoff in the Wujiang River watershed was simulated by a GIS-based method using precipitation, hydrology data, and land-use data. The volume of surface runoff is chiefly controlled by climates, topographical characteristics and types of land use at the watershed. Five subwatersheds that can represent the whole watershed were chosen and their average annual precipitation, average annual surface runoff and current land use were calculated respectively in the grid model of the Wujiang River watershed based on the climate and hydrology data from 1965 to 2000 and the land-use data acquired in the year of 2000. Surface runoff is assumed to be a function of precipitation and land use and the multiple regression tool is used to determine the relationship between surface runoff, precipitation and present land use. Thus, the rainfall-runoff model for each land-use type has been established. When calibrating these models, the results show that the percent errors are all below 7%, which indicates that the accuracy of this simulation is high.