Prioritization of sub-watersheds for conservation measures in a semi arid watershed using remote sensing and GIS

Land and water resources development plans are generally adopted at watershed level. Delineation of watersheds and their prioritization within large river basins requires host of terrain parameters to be studied and analysed. Chopan watershed in Central India has been studied for sub-watershed delineation and prioritization based on drainage morphometry, land use/land cover and sediment yield index analysis using remote sensing and GIS techniques. The watershed was demarcated into five sub-watersheds on the basis of drainage flow directions, contour value, slope, elevation. Geocoded satellite data of 1989 and 2001 on 1:50 000 scale were visually interpreted to prepare land use/land cover and drainage maps which were later digitized using Arcview/ArcGIS. Linear and shape aspects of the sub-watersheds were computed and used for prioritization. The results show widespread variation in drainage characteristics, land cover changes and sediment yield rates across sub-watersheds. On the basis of morphometric, land use/land cover change and sediment yield index, sub-watersheds were grouped into low, medium and high priority. A correlation of results show that SW1 and SW5 are common sub-watersheds falling under high and low priority based on morphometric, land use change analysis and SYI. The priority list of sub-watersheds will be crucial for decision making and implementation of land and water resource conservation projects.     

Watershed prioritization using morphometric and land use/land cover parameters: A remote sensing and GIS based approach

Jaggar watershed is a constituent of the Gambhir river basin, in eastern Rajasthan and covers an area of 352.82 km², representing arid climate. The drainage network is dendritic to sub-dendritic pattern however parallel to sub-parallel has also developed locally. The Jaggar watershed has been divided into fourteen sub-watersheds, designated as SW1 to SW14, for prioritization purpose. The prioritization of the sub-watersheds has been done on the basis of morphometric analysis and land use/land cover categories. Various morphometric parameters (linear and shape) have been determined for each sub-watershed and assigned rank on the basis of value/relationship with erodibility so as to arrive at a compound value for final ranking of the sub-watersheds. Land use/land cover mapping has been carried out using IRS LISS III data of 1998. Based on morphometric and land use/land cover analysis and their ranks, the subwatersheds have been classified into four categories as very high, high, medium and low in terms of priority for conservation and management of natural resources. The prioritization results based on morphometry reveal that only SW7 and SW10 fall under very high priority, whereas SW6, SW11 and SW13 fall under very high priority on the basis of land use/land cover analysis. However on the integration of morphometry and land use/land cover only SW14 show common priority whereas rest have little or no correlation.     

Terrain evaluation through the assessment of geomorphometric parameters using DEM and GIS: case study of two major sub-watersheds in Attapady, South India

Spatial pattern of geomorphometric parameters of two sub-watersheds in the Attapady valley, Kerala, is evaluated using the Geographical Information System. Both the aspatial and spatial morphometric and hypsometric measurements of the sub-watershed are compared. The analysis of geomorphometric parameters coupled with DEM and GIS suggests that the two sub-watersheds are structurally complex with high relief and the denuded hills are undergoing severe soil erosion. Terrain analysis enables evaluation of landform changes in the two sub-watersheds which indicate differences in the denudational history of adjoining watersheds. It is demonstrated that the domainal variations in the lithology and structural complexity are reflected in differences in the denudational history which in turn is manifested in the geomorphic parameters. The study also helps in developing functional relationships between geomorphometric parameters and hydrological variables.     

Remote sensing and GIS based comparative morphometric study of two sub-watershed of different physiographic conditions,West Godavari District,A.P.

In this present study, Remote Sensing (RS) and Geographical Information System (GIS) techniques were used to update drainage and surface water bodies and to evaluate linear, relief and aerial morphometric parameters of the two sub-watersheds viz. Jilugumilli and Regulapadu in the northern part of West Godavari District, Andhra Pradesh. The area of Jilugumilli and Regulapadu watersheds spread over about 110 & 80 sq. km respectively. The morphometric analysis of the drainage networks of Regulapadu and Jilugumilli sub-watersheds exhibit sub-dendritic and sub parallel drainage pattern. The variation in stream length ratio changes due to change in slope and topography. It was inferred from the study that the streams are in a mature stage in Regulapadu and Jilugumilli watersheds, which indicated the geomorphic development. The variations in bifurcation ratio values among the sub-watersheds are described with respect to topography and geometric development. The stream frequencies for both sub-watersheds exhibit positive correlation with the drainage density, indicating increase in stream population with respect to increase in drainage density. The Jilugumilli watershed has a coarse drainage texture and Regulapadu sub-watershed is a fine drainage texture in nature. In the present study an attempt has been made to analyse the morphometric analysis of two sub-watersheds under different physiographic conditions. Morphometric analysis is one of the essential analyses required for development and management of watershed.     

Soil Erosion Susceptibility Assessment of the Lower Himachal Himalayan Watershed

Assessment of erosion status of a watershed is an essential prerequisite for integrated watershed management. It not only assists in chalking out suitable soil and water conservation measures to arrest erosion and conserve water but also helps in devising best management practices to enhance biomass production in watersheds. Keeping this in view, the present study has been undertaken by involving geospatial-statistical techniques to determine the critical and priority areas for soil and water conservation in Suketi watershed of the lower Himachal Himalayan region. A novel weighted sum analysis technique was used for ranking each of hydrological unit by obtaining the weightages from various morphometric parameters. This technique offers dynamic, effective and sustainable approach over traditional prioritization methods in which significance of each parameter were considered equally. Considering this approach, sub-watersheds were delineated into low, medium and high priority zones. The results illustrate that about 52 % of sub-watersheds of Suketi watershed are in moderate to high erosion and runoff susceptible zones. Therefore, these potential areas can be considered for preferential soil and water conservation planning. The results obtained from the study will be useful for various stakeholders such as agriculturists, water resource managers, conservation measures planners and decision policy makers for better management practices and decision making. The geospatial-statistical technique can be used for effective estimation of erosion status of watersheds leading to watershed prioritization for taking up soil and water conservation measures in watershed systems. Finally, this technique can be very useful in remote, rugged and inaccessible watersheds with absence of soil erosion and runoff monitoring.     

基于GIS/RS的流域水文过程分布式模拟——Ⅱ模型的校检与应用

GIS/RS是流域水文过程分布式模拟的重要技术支撑。结合泾河流域的实例研究,探讨了GIS支持下,基于栅格DEM流域水文特征的获取,降水、气温等资料的空间插值,以及土壤、植被等下垫面信息在水文模拟单元上的耦合。在此基础上,应用分布式水文模型对泾河流域的水文过程进行模拟。结果表明:所建模型结构上是合理的,在产流计算中泾河25个子流域在水量平衡方面误差均小于5%。潜在蒸发的模拟在趋势上与实测过程基本一致。径流模拟在4个检验站点上与实测过程的相关系数达到0.84～0.93。模型基本能够满足水资源规划与管理的需要。     

基于DEM的流域降雨径流模拟——以蒲石河流域山区为例

DEM是目前用于流域地形分析的主要数据,基于DEM的水文模拟技术,在流域地形分析及水系构建等方面已形成了比较成熟的算法,给传统的水文模拟技术带来了根本性的变化。以蒲石河流域山区为例,借助流域水文软件WMS,结合ARCVIEW和SURFER软件,计算了流域的面积、周长、坡度与形状因子等参数。在生成山区数字高程模型的基础上,采用WMS嵌入的HEC-1模型对一场降雨进行了降雨径流模拟研究。     

Characteristics and driving factors of surface water chemistry of Wujiang watershed

The changes in the water chemistry of rivers can reflect influence of anthropogenic activities on the water environment to some extent. To understand the relationship between the spatial distribution of the eco-environment of the watershed and the characteristics of water chemistry and geochemistry of rivers, firstly, the digital Wujiang watershed was built, and then the sub-watersheds were delineated, taking the sample points as sub-watershed outlets based on GIS. Secondly, using the function of spatial analyst of GIS, the statistical features of eco-environment (such as lithology and land use/cover) of each sub-watershed were calculated according to their respective classification. Finally, the correlation between the spatial distribution of lithology of the sub-watersheds and their corresponding ⁸⁷Sr/⁸⁶Sr ratio of river water, the correlation between NO₃ ⁻/HCO₃ ⁻, Cl⁻/HCO₃ ⁻, SO₄ ²⁻/HCO₃ ⁻ and anthropogenic activities, respectively, and the correlation between the fraction of green vegetation of the sub-watershed and their corresponding flux of TDS (total dissolved solids) were analyzed quantitatively. The results justify that the ⁸⁷Sr/⁸⁶Sr ratio of river water is highly dependent on the lithologic feature of the watershed and indicate that anthropogenic activities are one of the main sources of NO₃ ⁻ and SO₄ ²⁻ of river waters. The output of TDS is highly dependent on the percentage of vegetation cover of the watershed.     

福建晋江流域锰负荷分布及源区识别

以福建晋江流域锰元素为研究对象,将整个流域划分为60个子流域并在各子流域出口处设置水质监测断面,分别于丰水期和枯水期对断面锰浓度进行取样测试,研究锰浓度的时空分布特征。结合流量监测和降水资料,利用水文比拟法计算并总结锰负荷的空间分布,基于锰负荷贡献率进行了锰源区识别。结果表明：丰水期锰浓度普遍高于枯水期,西溪锰浓度总体高于东溪。受矿山开采影响,全年锰浓度最大值位于上游双溪与大畬溪交汇处。锰负荷丰水期远高于枯水期,且具有随径流向下游聚集的趋势,最大值位于晋江流域最下游入海口断面。识别出的锰源区主要位于西溪流域以及干流下游临入海口子流域,应在今后的环境综合治理工作中重点关注。     

Hypsometric analysis and watershed management of Diyung watershed in north eastern India

The Diyung river descends in Nagaon district of Assam. After its confluence with main channel Kopili it causes enormous losses to life and property due to floods. Appropriate watershed treatment measures are, therefore, required for moderating the flood damage. In the present study landscape information viz., the hypsometric integral has been analysed. The Diyung watershed has been subdivided into 23 sub-watersheds for hypsometric analysis. The hypsometric integral for the entire Diyung watershed ranged from 0.14 to 0.56. According to the present study there are two stages of geologic/geomorphologic development, namely equilibrium stage and monadnock stage. The hypsometric integral indicates that surface runoff is the dominant process. Although static, the topographic characteristics indicate response of watershed to various natural phenomenon and dominant processes such as runoff and erosion. Based on the intensity of the processes sub-watershed can be prioritized for taking up appropriate conservation measures. The study also highlights the use of hypsometric integral for prioritizing watershed for planning engineering measures to mitigate the impact.     

Morpho-hypsometric evolution of the Karuvannur River Basin,a tropical river in central Kerala,southwestern peninsular India

An integrated morphometric and hypsometric analysis coupled with asymmetric factor used as a proxy for the landscape evolution of the catchment of Karuvannur River. The present study area is a sixth order tropical river in the central Kerala which supplies water and sediments to the Vembanad-Kol Ramsar site. The Karuvannur River Basin (KRB) has been divided into six sub-watersheds (SW). Morphometric parameters (areal, linear, and relief) and hypsometric and asymmetric factors are measured for the delineation of morphotectonic evolution of the area. High values of drainage density, texture, ruggedness number, and hypsometric integral with relatively high volume of leftover rocks in the basin in SW-II and SW-III compared to the entire basin of KRB imply that these two sub-watersheds have been influenced by the tectonic activities. Further, detailed asymmetric data indicated that these two watersheds are tilted in opposite direction. It may be the result of reactivation of Precambrian fault/lineament in recent past. This has been supported by recent tremors and neotectonic studies in Kerala. Moreover, detailed field evidence along with google imagery revealed that the entire basin is a part of regional anticline associated with PCSZ. Geomorphic response to disturbance will produce a sensible, recognizable response; it can be well studied in rivers through detailed study of their sensitivity or behavioral changes. Rivers have an enormous capacity to absorb perturbation and these types of studies are essential for identifying/measuring tectonic activities, sediment diffusion, surface runoff in a drainage basin, and as an important tool for target oriented micro watershed management.     

Using GIS-based distributed soil loss modeling and morphometric analysis to prioritize watershed for soil conservation in Bago river basin of Lower Myanmar

Bago River is an important river in Myanmar. Although shorter than other rivers, it has its own river system, and people along the river rely heavily on it for their daily lives. The upper part of the watershed has changed rapidly from closed forest to open forest land in the 1990s. Since the recent degradation of the forest environment, annual flooding has become worse during the rainy season in Bago City. This paper aims at determining soil conservation prioritization of watershed based on soil loss due to erosion and morphometric analysis in the Bago Watershed by integrating remote sensing and geographic information system (GIS) techniques. In this study, soil erosion of the Bago watershed was determined using the Universal Soil Loss Equation. Such factormaps as rainfall, soil erodibility, slope length gradient, and crop management were compiled as input parameters for the modeling; and the soil loss from 26 sub-watersheds were estimated. Then, the soil erosion maps of the Bago watershed for 2005 were developed. The resulting Soil Loss Tolerance Map could be utilized in developing watershed management planning, forestry management planning, etc.     

Prioritization of subwatersheds based on quantitative morphometric analysis in lower Bhavani basin,Tamil Nadu,India using DEM and GIS techniques

Watershed prioritization is one of the most important processes in natural resource management system especially in areas of sustainable watershed development and planning. Morphometric characteristics are the viable entity to understand the hydrological behavior of the subwatershed. For prioritization of subwatershed, morphometric analysis was utilized by using the linear, areal, and relief aspects of the drainage basin. In this context, remote sensing and GIS has been proved to be an efficient tool to identify the morphological features. The Survey of India (SOI) topographical maps, satellite data IRS-LISS III, and Cartosat DEM data were utilized to understand the drainage pattern and also for prioritization of subwatershed areas. The prioritization of subwatershed has been attempted using novel and quantitative approaches based on compound parameter ranking for soil erosion. Lower compound factors were chosen as the most feasible for soil erosion. Based on the observation, eight subwatersheds with a higher degree of the slope were severely prone to soil erosion and remaining 21 subwatersheds occur in low-lying areas that can be developed as sustainable watersheds. The identified subwatershed requires immediate soil remediation and water conservation measures for efficient watershed planning and management. The proposed study might be helpful for resource planners, government agencies, private sectors, and other stake holders to take up soil conservation measures and fixation of water-harvesting structures for better decision making.     

复杂山区小流域径流模拟影响因素分析

为探讨子流域划分与DEM分辨率对于地形和地表状况比较复杂的山区小流域径流模拟的影响,利用分布式水文模型SWAT(Soil and Water Assessment Tool)对复杂山区小流域进行径流模拟,从不同的子流域划分条件下分析了子流域划分对径流模拟的影响及其变化趋势.然后通过对原有的DEM(Digital Elevation Model)进行重采样生成不同格网大小的DEM作为模型输入,研究不同DEM分辨率对复杂山区小流域径流模拟的影响.研究表明:(1)存在一个比较合理的子流域划分方案使径流深比较稳定;(2)存在一个合适的DEM分辨率使模拟得到的径流深比较稳定;(3)山区复杂流域环境,要求更加精细的子流域划分才能获得(1)中的稳定径流深.     

Landslide susceptibility analysis using probabilistic likelihood ratio model—a geospatial-based study

The crucial and difficult task in landslide susceptibility analysis is estimating the probability of occurrence of future landslides in a study area under a specific set of geomorphic and topographic conditions. This task is addressed with a data-driven probabilistic model using likelihood ratio or frequency ratio and is applied to assess the occurrence of landslides in the Tevankarai Ar sub-watershed, Kodaikkanal, South India. The landslides in the study area are triggered by heavy rainfall. Landslide-related factors—relief, slope, aspect, plan curvature, profile curvature, land use, soil, and topographic wetness index proximity to roads and proximity to lineaments—are considered for the study. A geospatial database of the related landslide factors is constructed using Arcmap in GIS environment. Landslide inventory of the area is produced by detailed field investigation and analysis of the topographical maps. The results are validated using temporal data of known landslide locations. The area under the curve shows that the accuracy of the model is 85.83%. In the reclassified final landslide susceptibility map, 14.48% of the area is critical in nature, falling under the very high hazard zone, and 67.86% of the total validation dataset landslides fall in this zone. This landslide susceptibility map is a vital tool for town planning, land use, and land cover planning and to reduce risks caused by landslides.     

Neural network modeling for regional hazard assessment of debris flow in Lake Qionghai Watershed, China

This paper presents a neural network (NN) based model to assess the regional hazard degree of debris flows in Lake Qionghai Watershed, China. The NN model was used as an alternative for the more conventional linear model MFCAM (multi-factor composite assessment model) in order to effectively handle the nonlinearity and uncertainty inherent in the debris flow hazard analysis. The NN model was configured using a three layer structure with eight input nodes and one output node, and the number of nodes in the hidden layer was determined through an iterative process of varying the number of nodes in the hidden layer until an optimal performance was achieved. The eight variables used to represent the eight input nodes include density of debris flow gully, degree of weathering of rocks, active fault density, area percentage of slope land greater than 25° of the total land (APL25), frequency of flooding hazards, average covariance of monthly precipitation by 10 years (ACMP10), average days with rainfall >25 mm by 10 years (25D10Y), and percentage of cultivated land with slope land greater than 25° of the total cultivated land (PCL25). The output node represents the hazard-degree ranks (HDR). The model was trained with the 35 sets of data obtained from previous researches reported in literatures, and an explicit uncertainty analysis was undertaken to address the uncertainty in model training and prediction. Before the NN model is extrapolated to Lake Qionghai Watershed, a validation case, different from the above data, is conducted. In addition, the performances of the NN model and the MFCAM were compared. The NN model predicted that the HDRs of the five sub-watersheds in the Lake Qionghai Watershed were IV, IV, III, III, and IV–V, indicating that the study area covers normal hazard and severe hazard areas. Based on the NN model results, debris flow management and economic development strategies in the study are proposed for each sub-watershed.     

Prioritization of Malesari mini-watersheds through morphometric analysis: a remote sensing and GIS perspective

Geographical information system and remote sensing are proven to be an efficient tool for locating water harvesting structures by prioritization of mini-watersheds through morphometric analysis. In this study, the morphometric analysis and prioritization of ten mini-watersheds of Malesari watershed, situated in Bhavnagar district of Saurashtra region of Gujarat state, India, are studied. For prioritization of mini-watersheds, morphometric analysis is utilized by using the linear parameters such as bifurcation ratio, drainage density, stream frequency, texture ratio, and length of overland flow and shape parameters such as form factor, shape factor, elongation ratio, compactness constant, and circularity ratio. The different prioritization ranks are assigned after evaluation of the compound factor. Digital elevation model from Shuttle Radar Topography Mission, digitized contour, and other thematic layers like drainage order, drainage density, and geology are created and analyzed over ArcGIS 9.1 platform. Combining all thematic layers with soil and slope map, the best feasibility of positioning check dams in mini-watershed has been proposed, after validating the sites through the field surveys.     

Hypsometric analysis of Shakkar river catchment through geographical information system

Hypsometric analysis of watershed (area-elevation analysis) has generally been used to reveal the stages of geomorphic development (stabilized, mature and young). The geologic stages of development and proneness of the watersheds for erosion are quantified by hypsometric integral. The estimation of hypsometric integral is carried out from the graphical plot of the measured contour elevation and encompassed area by using empirical formulae. In this study, efforts were made to estimate the hypsometric integral values of Shakkar river watershed which is a tributary of Narmada river located in Madhya Pradesh. The watershed was delineated into eight sub-watersheds and hypsometric analysis was carried out for all of them using digital contour maps, which was generated using Arc/Info GIS. The hypsometric integral values for all the sub-watersheds of Shakkar river ranges between 0.47 and 0.51. In the study area, only mature stage of erosion cycle is identified.     

Contribution of aluminum from abandoned surface mine pits in Raccoon Creek, Ohio

Middleton Run, a severely acid mine drainage (AMD) impacted tributary of Little Raccoon Creek, drains a sub-watershed area of 3.67 km² (2.28 square miles). Averaging 58.7 kg/day (129.4 lbs/day) at its mouth, demonstrated aluminum loads from Middleton Run are particularly severe. A preliminary study of two previously unmonitored tributaries was conducted to justify future treatment projects. Monthly chemical water quality data were collected for 6 months. Soil leachate samples collected on five strip mining sites within the sub-watershed were analyzed for acidity, alkalinity, pH, aluminum and iron. Soil leachate tests have shown that one of the pits has a much larger pollution production potential and should be targeted for remediation.     

Earth Observations based Conservation Prioritization in Western Ghats,India

Earth Observation with large suite of sensors and with capabilities to address natural resources at multiple scales has proven to be a critical resource in setting conservation priorities of a region. The role of earth observation data was recognized towards achieving international biodiversity targets by 2020. Ecosystem irreplaceability and ecosystem vulnerability are two concepts key to understanding and preparing conservation priority maps. This study presents spatial conservation prioritization analysis for forests of ‘Western Ghats biodiversity hotspot’. Earth observation data products have been used for prioritization of areas of irreplaceability and vulnerability that are significant for conservation planning. The spatial surrogates of biodiversity in terms of very dense forest, biological richness, intactness and rarity of habitat are analyzed for evaluation of ecosystem irreplaceability. Fragmentation, forest fires, plant invasion and disturbance index are surrogates included for spatial analysis of ecosystem vulnerability. Vegetation type wise analysis indicates dry deciduous forests are under high vulnerability, followed by moist deciduous forests. The high concentration of irreplaceability is observed in Shola followed by wet evergreen forests and semi-evergreen forests. Spatial prioritization approach has identified about 18% of the forest area as irreplaceable which represents overlapped area of very dense forest, shola, intact forest and high biological richness. We observed that the overlap of forest areas of irreplaceability with vulnerability in southern Western Ghats, which needs high priority of conservation. This study is the first of its kind wherein multi-source earth observation data has been analysed to examine the quantitative criteria at regional level in Western Ghats.