Watershed Prioritization of Palar Sub-watershed Based on the Morphometric and Land Use Analysis

Morphometric analysis is an indispensable tool for hydrological investigation that involves the development and management of drainage basin. This study characterizes the micro watersheds in the Palar sub-watershed using morphometric analysis and assesses its risk by land use and land cover features in a particular micro watershed. Palar sub-watershed is divided into 6 micro watersheds for prioritization based on morphometric and land use analysis. Several morphometric parameters （linear, shape and relief） are determined from the drainage map; ranks are assigned based on their capacity to induce erodability and degradation. Final ranking is based on the composite index calculated from the sum of the ranks of each morphometric parameter. Morphometric analysis reveals micro watersheds 5 and 6 as most susceptible and 2 and 3 as low susceptible. Land use is mapped using IRS ID LISS III satellite data. The risk in terms of watershed degradation involved to each micro watershed is based on the ranks of each land use feature, obtained from a similar composite index as that of morphometric analysis. Land use analysis shows that micro watersheds 2 and 4 fall under high priority category while 5 and 6 under low priority category. Integration of the morphometric and land use analysis shows that only microwatershed 1 falls under the same category in both analyses. Control measures are suggested to contain degradation depending on its specific land use pattern and morphometric features. This study ean be used to prepare a comprehensive watershed plan for the development or for planning resource conservation strategies, by integrating land use features with the drainage characteristics of the region, in particular for a hill ecosystem as the prioritization is at micro level.

Ranking the Suitability of Sub-watersheds for Ponding-Based Methods of Managed Aquifer Recharge in Lower Yom River Basin, Thailand

The study area is located in the Lower Yom River Basin covering an area of about 970 km^2 in the lower part of Northern Thailand, which is underlain by sequences of unconsolidated alluvial deposits derived from the Yom and Nan River floodplains. Groundwater has been heavily exploited largely for agriculture from the shallow gravel, sand and silt aquifer in the basin. Drastically declining water levels, up to 10 m in some areas, has been observed within the past decade, creating difficulties with lift irrigation for the local farmers. Therefore, the Department of Groundwater Resources, Thailand, considers that groundwater artificial recharge may be useful for recovering the static water levels within the most hydrogeological suitable areas. The objective of the paper is to rank the suitability of sub-watershed in the Lower Yom River Basin for conducting a pilot-scale testing of MAR （managed aquifer recharge） by ponding system. Hydrogeological and non-hydrogeological parameters were used to formulate the site selection criteria. Boolean logic and Fuzzy logic were used for delineating the 19 sub-watersheds in the Lan Ba watershed. Detailed hydrogeological investigations were conducted in the 10 most prospective sub-watersheds. Of these, the Nong Na 3 sub-watershed covering an area of about 500 hectares was determined to be the most appropriate site for the MAR pilot construction and testing.

Multi-criteria decision analysis for sub-watersheds ranking via the PROMETHEE method

Soil and water resources are important elements of the environment that is managed to reduce the erosion rate and the destructive effects of torrential flooding.Implementation of the measures to reach this goal requires the ranking of sub-watersheds and areas within the sub-watersheds,from most to least vulnerable,which can be achieved using Multi-criteria decision analysis methods.In this paper,using the Preference Ranking Organization Method for Enrichment Evaluations(PROMETHEE)Ⅱ method ranking of nine sub-watersheds delineated in the Topciderska river watershed,Serbia,was performed by using ArcGIS software.The criteria used for determining the order of the most vulnerable sub-watersheds are land cover,rainfall,soil erodibility as well as topography.The importance of criteria was determined by using the Analytic Hierarchy Process(AHP)method,and the influence of the criteria weights on ranking results was tested.This research identified that the most vulnerable sub-watershed is located in the upper part of the study area,where 15% of the territory is at high risk of erosion.Thus,this sub-watershed should have priority for protection through the implementation of appropriate measures and works.The results of the PROMETHEE Ⅱ method and the ArcGIS application represent the valuable information for watershed management planning and implementation of soil erosion and torrent control measures.

Watershed classification by remote sensing indices： A fuzzy c-means clustering approach

Determining the relatively similar hydrological properties of the watersheds is very crucial in order to readily classify them for management practices such as flood and soil erosion control. This study aimed to identify homogeneous hydrological watersheds using remote sensing data in western Iran. To achieve this goal, remote sensing indices including SAVI, LAI, NDMI, NDVI and snow cover, were extracted from MODIS data over the period 2000 to 2015. Then, a fuzzy method was used to clustering the watersheds based on the extracted indices. A fuzzy c-mean(FCM) algorithm enabled to classify 38 watersheds in three homogeneous groups.The optimal number of clusters was determined through evaluation of partition coefficient, partition entropy function and trial and error. The results indicated three homogeneous regions identified by the fuzzy c-mean clustering and remote sensing product which are consistent with the variations of topography and climate of the study area. Inherently,the grouped watersheds have similar hydrological properties and are likely to need similar management considerations and measures.

Effects of sustainable land management interventions on selected soil properties in Geda watershed,central highlands of Ethiopia

Background:Land degradation through soil erosion by water is severe in the highlands of Ethiopia.In order to curb this problem,the government initiated sustainable land management interventions in different parts of the country since 2008,and in Geda watershed since 2012.However,the impacts of the interventions on soil properties were not assessed so far.Thus,this study investigated the impacts of sustainable land management interventions on selected soil properties in Geda watershed.Soil samples were collected from treated and untreated subwatersheds at the upper and lower landscape positions,from cropland and grazing lands at two soil depths(0-15 cm and 15-30 cm).Selected soil physicochemical properties were assessed with respect to landscape position,land-use type,and soil depth in both treated and untreated sub-watersheds.Results:Generally,most of the soil physicochemical properties differed greatly across sub-watersheds,land-use types,and soil depths.Clay,electrical conductivity,total N,available P,exchangeable K,and organic carbon were higher in the treated sub-watershed,whereas sand,silt,bulk density,and pH were higher in the untreated subwatershed.The higher sand,silt,and bulk density could be attributed to erosion,while the higher pH could be due to the higher exchangeable Na in the untreated sub-watershed.Most of the selected soil chemical properties were not affected by landscape position,but land-use type affected available P and organic carbon with higher mean values at croplands than at grazing lands,which could be ascribed to the conservation structure and tillage of the soils in that conservation structures trap and accumulate transported organic materials from the upper slope,while tillage facilitates aeration and decomposition processes.Conclusion:Sustainable land management interventions improved soil physicochemical properties and brought a positive restoration of the soil ecosystem.Maintaining the soil conservation measures and enhancing community awareness about the benefits,coupled with management of livestock grazing are required to sustain best practices.

Sustainable land management interventions lead to carbon sequestration in plant biomass and soil in a mixed croplivestock system:the case of Geda watershed,central highlands of Ethiopia

Background:Sustainable land management interventions were introduced in Geda watershed in 2012 to reduce soil erosion,improve water infiltration,and increase plant-carbon inputs into the soil.This study explored the impact of the interventions on biomass production,carbon stock,and carbon sequestration.Stratified sampling was employed in the main and the dry seasons in the treated and untreated sub-watersheds that are found adjacent to each other.Above-and below-ground plant biomass,soil bulk density and organic carbon in 0-15-and 15-30-cm depths,and soil moisture content in 0-20-and 20-40-cm depths were collected from the crop,grazing,and tree lucerne plots.All analyses were performed based on standard procedures.Results:Plant biomass production,carbon stock,and carbon sequestration varied highly significantly(P≤0.001)among sub-watersheds,landscape positions,and land uses.Higher mean values were observed for treated subwatershed,lower landscape position,and tree lucerne plot.The higher mean values in the lower landscape position of the treated sub-watershed were due to tree lucerne plantation.Similarly,topsoil(0-15 cm)carbon stock was statistically higher(P≤0.001)in the treated sub-watershed and at tree lucerne plot(P≤0.05).In addition,carbon stock by sub-surface soil(15-30 cm)was significantly higher(P≤0.001)in the treated sub-watershed under crop and grazing lands but the higher value was in cropland and in the upper position.This could be due to the decomposition of organic materials from biomasses of crops and biological supporting measures(tree lucerne and Phalaris)facilitated by tillage.Six years of sustainable land management interventions led to the sequestration of 12.25,7.77,and 13.5 Mg C ha^(−1) under cropland,tree lucerne,and grazing plots,respectively.Conclusion:Sustainable land management interventions revealed auspicious ecological impacts in Geda watershed in terms of improving plant biomass production,carbon stock,and correspondingly capturing higher carbon dioxide equivalent taking untreated sub-watershed as a baseline.Prohibition of free grazing was the key element of the intervention to reduce biomass export and increase carbon sequestration in the treated sub-watershed.Thus,sustaining tree lucerne plants as a conservation measure and the prohibition of free grazing practices are principally essential.