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.

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.

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.