Soil And Water Conservation Structures Research Articles

Prioritization of sub-watersheds and subsequent site identification for soil water and conservation practices using the SWAT-AHP integrated model in the Lower Sutlej Sub-basin, India.

Prioritization of watersheds is a crucial step in integrated river basin management. It guides resource allocation, planning, decision-making, stakeholder engagement, targeted interventions, and monitoring and evaluation efforts. By identifying and addressing priority watersheds, comprehensive and sustainable management of water resources can be achieved within a river basin. The aim of the current study is to prioritize watersheds using the Soil and Water Assessment Tool (SWAT) and site suitability analysis for the implementation of soil and water conservation structures (SWCS) in the prioritized watersheds by using an analytical hierarchy process (AHP) of the Lower Sutlej Sub-basin, India. The model was calibrated with observed data from 2017 to 2019 with the first 2years (2015-16) as a warm-up period. Furthermore, validation of the model was done using 2-year data from 2020 to 2021. The model showed successful performance in terms of the R2 range from 0.72 to 0.89, the NSE range from 0.67 to 0.73, the PBIAS range from - 26.70 to 11.30, and the RSR range from 0.51 to 0.57 for stream flow and sediment yield during calibration and validation period. The basin's average annual soil loss ranged from 3.08 to 21.63 t/ha/year, a watershed with the WS2 index seeing the highest rate of soil erosion (21.63 t/ha/year). Hence, WS2 was found to be a top priority. In addition, the site suitability analysis of the prioritized watershed (WS2) reveals that about 1.42% of the area is extremely suitable, 16.14% is highly suitable, and 35.58% is moderately suitable for SWCS. According to the site suitability map validation, both dam locations were found in highly suitable areas, so the developed site suitability map is accurate. This research will help sustainability planners and managers make more informed decisions when building SWCS at suitable sites for better land and water conservation.

Impact of soil and water conservation structures on the spatial variability of topsoil moisture content and crop productivity in semi-arid Ethiopia

Plant available soil moisture and its spatial variability is among the most important limiting factors for crop and livestock productivity in semi-arid Ethiopia. The objectives of this study were therefore: 1) to measure the effects of land use and slope gradient on spatial variability of topsoil moisture content. 2) to analyze the variability of topsoil moisture content and crop responses under different soil and water conservation (SWC) structures and 3) to analyze whether topsoil moisture content, grain and biomass yields vary in relation to SWC structures. In total, 21 large runoff plots (600–1000 m2) were installed and treated with stone bunds, trenches, stone bunds with trenches and a control plot at each site. Plot sites were located on gentle (5%), medium (12%) and steep (16%) slopes of cropland and rangeland. Topsoil (0–15 cm) moisture content for plots were monitored daily using soil moisture probes (Theta-Probes) and weekly using manual sampling over two growing seasons. Crop performance was monitored during two growing seasons and grain and biomass yield were measured at harvest. Results show that average gravimetric moisture content of the topsoil during growing seasons is remarkably higher for cropland (33–25 g/100 g) compared to rangelands (24–20 g/100 g). This is due to tillage-induced runoff retention and infiltration. Soil moisture content decreases with increasing slope gradients, owing to increased drainage. Considering the effects of SWC structures, average topsoil moisture contents at accumulation and erosion zones are generally higher as compared to middle zone between two successive SWC structures. Average seasonal volumetric soil moisture content of 38.2 (cm3/100 cm3) in 2011 and 39.4 (cm3/100 cm3) in 2012 for accumulation zone of plots with stone bunds with trenchers are significantly higher than at other sampling locations. Crop growth performance, grain and biomass yield varied among plots and depended on slope gradients and SWC structures. Grain yields of wheat in 2011 and barley in 2012 were significantly higher for plots with SWC structures as compared to control plots and are highly correlated to topsoil moisture content (r = 0.64; p < 0.04 in 2011 and r = 0.59, p < 0.01 in 2012). Even when taking into account the cropland area occupied by SWC structures, grain yield increased by (4.2%−33%) for plots with SWC structures as compared to control plots. Overall, our results show that implemented measures may not only reduce runoff and soil loss, but also increase crop productivity by enhancing soil moisture and thus can significantly contribute to sustainability of agro-ecosystems in semi-arid environments.

Assessing the impacts of soil and water conservation practices on soil physicochemical properties in contrasting slope landscapes of Southern Ethiopia

In Ethiopia in general and in the study area, soil erosion, which is the main cause of land degradation, is a significant environmental and agricultural problem. The efficiency of various land management strategies used over time to reduce their detrimental effects on soil quality and health has been questioned. The purpose of this study was to determine the efficacy of soil and water management methods applied to the Offa District of the Wolaita Zone in southern Ethiopia. A total of 36 composite and core soil samples were taken from the topographies of both conserved and non-conserved fields from the top 20 cm soil depth. The collected soil data were examined using analysis of variance (ANOVA), and the mean values of the treatments were separated using the Fisher multiple range test. The results revealed that the physical and chemical properties of soil (pH, Organic carbon, Total nitrogen, Available phosphorus, Cation exchange capacity (CEC), exchangeable basic cations (Ca2+, Mg2+, K+, and Na+), Soil texture, and Bulk density showed a significance difference (p < 0.05) between the measures of soil and water conservation (SWC). The treated soils of Fanya juu, stone bund, and soil bund had the highest soil pH (6.56, 6.56, and 6.11), organic carbon (1.80, 1.62, and 1.76 %), total nitrogen (0.18, 0.16, and 0.17 %), accessible phosphorus (2.72, 2.77, and 1.94 ppm), and all exchangeable basic cations showed higher amount than untreated. The results showed that the implemented SWC structures had high value in restoring and preserving soil nutrients and improving the productive capacity of the soil. This study confirmed the effectiveness of SWC practices in improving soil quality. To achieve soil quality, it's essential to maintain awareness and use of the latest technology. It is strongly advised to highlight the urgent need for SWC training, public awareness, and government support.

Estimating the runoff response from hillslopes treated with soil and water conservation structures in the semi-arid Ethiopian highlands: Is the curve number method applicable?

Planning and management of water resources is crucial to enhance agricultural productivity and ensure food security in drylands. For this, adaptable and reliable runoff prediction models are urgently needed to support water harvesting and irrigation development. In this study we explored the potential of the runoff Curve Number (CN) method to estimate daily surface runoff from representative land use types and management conditions in Tigray (north Ethiopia). For this, we use the National Engineering Handbook (NEH-Tables) to derive CN values for runoff plots treated with and without soil and water conservation (SWC) structures. Moreover, the rainfall-runoff data collected from 21 large (600–1000 m2) runoff plots during three years (2010 to 2012) were used to calculate CN-values. Results show that CN values derived from the NEH-Tables are larger by 21% compared to those values calculated from plot data. The calculated CN values vary widely (34 to 91) in response to land use type, slope gradient, and applied SWC structures. Our results show that land use and SWC structures strongly influence runoff production. Considering plots with otherwise similar characteristics, CN values are consistently larger for rangeland sites as compared to those values for cropland sites. Likewise, SWC structures greatly reduce runoff production and their presence also leads to a clearly lower performance of the CN model. The results of this study are relevant contributions towards addressing several goals of agenda 2063 of the African union either directly or indirectly and also international sustainable development goals (SDG). Based on our analysis and field observations, we propose calibrated CN values that may be used for runoff yield assessments in similar environments.

Sustainability of the long-term indigenous soil and water conservation practices in the UNESCO designated cultural landscapes of Konso, Ethiopia

The role of sociocultural values and indigenous institutions in the sustainability of soil and water conservation (SWC) practices has not been well addressed in previous studies. Therefore, this study explores the role of sociocultural values and indigenous institutions in the sustainability of SWC practices in Konso, Ethiopia. The study used key informant interviews, focus group discussions, and participant observations to collect data. The data were coded and analyzed thematically. The study shows that sociocultural values, cooperative labor groups, and indigenous institutions served as the backbone for the sustainability of indigenous SWC practices for many years. However, recent trends in urbanization and the introduction of modern administration have led to a gradual weakening of Konso indigenous institutions and sociocultural values. The introduction of modern administration and urbanization significantly reduced the role of indigenous sociocultural and political institutions. The study also indicates that a persistent decline in farmland productivity due to erratic rainfall is threatening the sustainability of SWC practices as it has forced the youth to engage in off-farm activities. When crops fail due to unreliable rainfall, some family members temporarily migrate to some towns in southern Ethiopia in search of jobs. Consequently, SWC structures remain unmaintained on some farmland for a season. Weakening of indigenous political institutions and sociocultural values, erratic rainfall, and recurrent droughts lead to the deterioration of SWC practices. Therefore, to ensure the long-term sustainability of indigenous SWC practices in Konso, the government and conservation NGOs should support socio-cultural institutions to restore and promote social norms, values, and indigenous conservation measures.

Effectiveness of soil and water conservation structures in increasing community perception and controlling erosion and sedimentation

The increasing frequency of floods and landslides has prompted the Ministry of Environment and Forestry to intensify the construction of soil and water conservation (SWC) structures in various watersheds in Indonesia. However, the evidence on how the high-cost measure can effectively increase community perception and participation while controlling erosion and sedimentation is still limited. For this reason, this preliminary research was conducted in 2019 to observe community perception and assess the effectiveness of the SWC structures in controlling gully erosion and sedimentation. The activities carried out in the Jeneberang and Lisu Sub Watershedsconsisted of two parts: 1) social and economic data collectionand 2) observing the effectiveness of the SWC structures in controlling sedimentation. Based on the socio-economic survey, respondents in the Jeneberang showed a better understanding and higher incomes than respondents in the Lisu Sub Watershed, despite their lowereducation levels.These phenomena relateto the length of time the community has learnedfrom surrounding examples and the applied SWC techniques on their land.In terms of the effectiveness of SWC structures, more than half of the retaining dam and gully plug capacityhad been filled with sediment in just oneyear after construction and is expected to be full at the end of the rainy season.The leadingcause is the high erosion of the tillage area on both sides.As a suggestion, agricultural land in the catchment area needs to be managed by applying SWC techniques according to site conditions through incentives given to landowners.

Effects of Soil and Water Conservation Structures on Selected Soil Physicochemical Properties: The Case of Ejersa Lafo District, Central Highlands of Ethiopia

Land degradation in the form of soil erosion and fertility depletion is the major environmental problem in Ethiopia. However, to curb this problem, soil and water conservation (SWC) structures are commonly practiced in many rural parts of Ethiopia. This study was conducted to assess the effects of SWC structures on selected soil physicochemical properties in Ejersa Lafo district. For this study, two kebeles (peasant associations) were selected purposively from the district based on the severity of soil erosion and information on SWC practices. The research design employed in this study was systematic, randomized, complete block design. A total of 12 composite soil samples were collected from the depth of 0 to 20 cm at two subwatersheds, namely, Jamjam laga batu and Koriso Odo guba with SWC and without SWC structures at three landscape positions. All the soil samples were analyzed following the standard and recommended procedures. The effect of independent variables (SWC practices and landscape positions) on the dependent variables (soil properties) was statistically tested using the SPSS computer program 21. In this study, most of the selected soil physicochemical properties were affected by watershed management intervention (SWC) structures. Soil moisture content (SMC), clay, pH, electrical conductivity (EC), total N (TN), available (AP), available K (AK), and organic carbon (OC) were higher in the subwatershed treated with SWC structures (conserved), whereas bulk density, silt, and sand were higher in the subwatershed without SWC structures (nonconserved). Most of the selected soil chemical properties were significantly varied (p&lt;0.05) between conserved and nonconserved farm land except EC. All the selected soil physicochemical properties did not show any significant variation (p&lt;0.05) at landscape positions except sandy soil. The physicochemical soil properties of selected parameters were in good conditions in the conserved areas with higher N and OM and lower BD, indicating fertility of the soil compared with the nonconserved land. The implementation of SWC structures improved some of the physicochemical properties of soil, such as SMC, clay particle, pH, EC, total N, AP, AK, and OC in the study area. Furthermore, efforts are required to enhance community adoption towards soil and water conservation. Additionally, further research has to be carried out on socioeconomic aspects and impacts of the intervention on crop productivity for better understanding of the sustainable use of the land.

Exploring decision-making in campaign-based watershed management by using a role-playing game in Boset District, Ethiopia

CONTEXTThe sustainability of the ongoing national Campaign-Based Watershed Management (CBWM) program in Ethiopia is questionable due to poor planning and implementation practices. OBJECTIVEThis study analyzes farmers' decision-making in the CBWM program, and mutual learning and collective decisions among local actors in Boset District - Ethiopia. METHODSRole-Playing Game (RPG) was the main method of the study. In order to collect pertinent information during the game sessions, observation of farmers' behavior and group discussions were used. Descriptive statistics and qualitative analysis were employed to analyze game outputs. RESULTS AND CONCLUSIONSResults show that farmers prefer to collectively work on private farmlands rather than on communal land. Furthermore, participation of farmers in campaign works was higher under a default-scenario (with control instruments), than under a willingness-scenario (without control instruments). In making decisions on their level of participation in campaign works, farmers followed the decisions of a fellow farmer they considered more knowledgeable. However, the participation of farmers in the maintenance of Soil and Water Conservation (SWC) structures was more or less the same under both scenarios. Both farmers' level of participation in campaign works and maintenance decisions were influenced by their proximity to the CBWM intervention areas (i.e. micro-watersheds) as well as their awareness and motivation. The commitment of local government actors was also crucial to enforce and encourage the farmers to participate in the program. Based on farmers' decisions in the RPG, none of the two scenarios simultaneously enhance the total land area covered with SWC structures and income of farmers. An important benefit of this game was that it stimulated mutual learning and collective decisions on micro-watersheds to be treated and alternative management strategies for the CBWM program. This revealed that there is a need to (1) motivate farmers through capacity building, (2) enhance the commitment of local government actors, and (3) introduce participatory planning to enhance mutual learning and collective decisions for sustainable watershed management. SIGNIFICANCEWhile directly applicable to the study area, these recommendations and the RPG (as a toolkit) are essential to enhance the outcomes and sustainability of collective watershed management initiatives in other parts of the world.

Assessment of Design and Constraints of Physical Soil and Water Conservation Structures in respect to the standard in the case of Gidabo sub-basin, Ethiopia

In Ethiopia institutional and extensive soil and water conservation (SWC) started in the 1970s. Due to several factors, most SWC works have not fully achieved the intended objectives. The disparity between dimensions of the implemented SWC work and the standard is the main factor. Therefore, this research work aimed to assess the design and constraints of SWC in the Gidabo sub-basin, of the Ethiopian rift valley. Data were generated through field observation, field measurements, household survey, interview, group discussion, and Arc GIS. According to the result, about 47.3% of the physical design of the implemented SWC structures failed to meet the standard dimension. In addition, the SWC lacks the standard supportive activities, such as the cut of the drain, check dam, biological work, and frequent maintenance. FGD and KII showed about 71.3% of the farmers accepted SWC technologies, but they have constraints for SWC. These were small land size, food insecurity, lack of resources, technical skill, field guidance, poor maintenance, as well as young migration. The researchers used the chi-square test for the significant variation of constraints along with different agro ecology. According to the chi-square result, significant association was observed between land size, access to fertilizers, seeds, pesticides, construction materials, technical skill, and maintenance of the structures versus agro ecology. Therefore, the implementation of SWC practices should be focused on the way to avoid/lower the observed mismatch of the structures against the standard. Also the constraints in different agro ecology should be solved through full community participation in order to follow the standard SWC measures for sustainable socio-economic and environmental development.

Effect of Level Soil Bund and Fayna Juu on Soil Physico-chemical Properties, and Farmers Adoption Towards the Practice at Dale Wabera District, Western Ethiopia

The objective of this study was to evaluate the effect of physical soil and water conservation (SWC) structures and slope gradients on soil properties and to identify factors affecting farmer’s adoption of the SWC practices. Cropland treated with level soil bund, fanya juu, and adjacent cropland without conservation structures were considered along the three slope gradients. A total of 27 soil samples were collected from the top 20 cm soil depth in ‘X’ design square plot with a length of 10m x 10m and replicated three times. A total of 120 households (HH) were randomly selected among which 48.3% were adopters and 51.7% were non-adopters of SWC structures. The collected soil samples were analyzed following standard laboratory procedures and a total of 10 variables were fitted in the logistic regression model. The result of the analysis revealed that sand fraction (%), SOC (%), TN (%), CEC (meq/100gm), and pH (H2O) were showed significant (P ≤ 0.05) differences between cropland treated with conservation structures and control plots; however, available P (ppm) did not show significant (P ≤ 0.05) variation. With regard to slope gradient, soil textural fractions sand (%), Silt (%) and Clay (%), and CEC (meq/100gm) were showed significant difference (P ≤ 0.05). While BD (g cm-3), SMC (%), SOC (%), TN (%), and available P (ppm) did not significantly differ along the slope. The result of the model also showed that the explanatory variables; age, education level, family size, landholding, farm experience, availability of labor shortage, and extension service were significantly affected the adoption of SWC practices by the farmers. On the other hand; sex, marital status, and livestock holding were not significantly affected farmers’ adoption of SWC practice. Therefore, scaling up of the soil bund for the area is necessary and building capacity, providing training and experience-sharing through field days for farmers is essential. Moreover, further investigation is encouraged on the integrated effect of physical and biological SWC practice and its socioeconomic aspects for a better understanding of the effect of sustainable use of the land.

Comparative study on spatial variability of topsoil moisture content and carbon stocks as influenced by land use and soil and water conservation structures in the semi-arid Ethiopian highlands

ABSTRACT Land uses and soil and water conservation (SWC) structures affect topsoil moisture and carbon stocks, particularly in the water deficit semi-arid environment of the northern Ethiopian highlands. This study was undertaken to assess the effects of land use and SWC structures on topsoil moisture, biomass, and soil carbon. Soil moisture was measured manually using gravimetric methods and theta probes with data loggers. Vegetation was inventoried and soil samples collected to assess carbon stocks of biomass and soils of different land uses. Merebmiti catchment had higher average gravimetric soil moisture content (GSMC; 24%) in wetlands, with the lowest (13%) in exclosures, whereas Mayleba catchment had relatively higher GSMC (14%) in exclosures and the lowest (8%) in rangelands. In both catchments, GSMC was higher at sampling locations closer to SWC structures than farther away. Merebmiti had significantly more biomass carbon (28.9 Mg ha−1) than Mayleba (6.32 Mg C ha−1). Higher soil organic carbon stocks were found in exclosures (46.1 ± 2.20 Mg ha−1) and wetlands (62.1 ± 2.9 Mg ha−1) than in frequently cultivated croplands (24.3 ± 1.4 Mg ha−1). Effective management of land use and implementation of SWC structures remarkably improves topsoil moisture content and carbon stocks in these catchments.

Integrated impact assessment of soil and water conservation structures on runoff and sediment yield through measurements and modeling in the Northern Ethiopian highlands

Developing countries with an increasing population like Ethiopia experience degradation of land and water resources. To tackle this problem soil and water conservation (SWC) has been practiced and recently promoted by the Ethiopian government. However, the effectiveness of SWC practices on runoff and soil erosion have not been studied in detail for their long- and short-term effects. An integrated measurement and modeling study was conducted from 2012 to 2014 in the Gumara-Maksegnit sub watershed to assess the impacts of SWC structures on runoff and sediment yield using the Geospatial Interface for the Water Erosion Prediction Project (GeoWEPP) model. The study was conducted in two adjacent, smaller watersheds where SWC structures were constructed in one of the watersheds (treated sub watershed), while the other one was a control watershed without SWC structures (untreated sub watershed). The treated sub watershed has an area of 27.1 ha and the untreated sub watershed has an area of 31.7 ha. Runoff and sediment yield were compared based on the observations and GeoWEPP model simulations. The GeoWEPP model simulation results predicted the daily runoff satisfactorily for both sub watersheds (R2 = 0.68 and NSE = 0.43 for untreated and R2 = 0.61 and NSE = 0.84 for treated sub watershed). Similarly, the model prediction showed satisfactory results in sediment yield (R2 = 0.61 and NSE = 0.59 for untreated and R2 = 0.57 and NSE = 0.81 for treated sub watershed). SWC structures reduced slope gradient and changed flow accumulation. The observation and simulation study concluded that the treated sub watershed surface runoff was reduced by about 19% as compared to the untreated sub watershed. Similarly, the model estimated that SWC structures constructed in the treated sub watershed reduced the total area that generates soil loss above the set target limit of 10 t ha−1 y−1 from 49% to 38% of the watershed area. SWC has led to a significant reduction in sediment yield by 28 to 38% in these highland watersheds of Ethiopia. The results confirmed that SWC structures have a significant impact to prevent land degradation in the Ethiopian highlands.

Technical evaluation of soil and water conservation measures in Maego Watershed, North Ethiopia

Soil and water conservation (SWC) practices have been carried out to solve land degradation problems in Ethiopia since the last 3 decades. Technical evaluation of the implemented SWC structures is essential for effectiveness and sustainability of the measures. Therefore, the objective of this study was to identify and evaluate the technical quality of constructed physical SWC structures in Maego watershed, Ethiopia. The performance of the structures was evaluated based on technical standards set by Ethiopian Ministry of Agriculture. Parallel transect walk method was used to measure the dimensions of the structures. The major types of SWC structures constructed in the study watershed are stone bund, hillside terrace, bench terrace, stone bund/hillside terrace + trench and gabion check dams. Some of the structures, especially the old ones which are found on the uncultivated land did not meet the site specific width and height standards. Furthermore, some of the spacing of SWC structures was not set depending on the desired vertical intervals/slope. With similar biophysical features of the watershed, some of the structures were narrowly spaced and some others were spaced greater than the standard. Most of the structures, especially the old ones are filled by sediment deposition. The main reasons for the failure to achieve the technical quality based on the technical standards were knowledge and skill gaps, free grazing and more attention was given to coverage areas rather than technical quality at the beginning of the watershed treatment. Furthermore, there is no maintenance of the structures on the communal lands. Therefore, awareness creation for the local community and capacity building about layout of structures for the local technical leaders should be given. Moreover, more attention should be given to technical quality rather than coverage area of SWC structures.   Key words: Soil and water conservation, technical evaluation, Maego watershed.

Gully and soil and water conservation structure densities in semi‐arid northern Ethiopia over the last 80 years

AbstractGullies have been a common phenomenon in semi‐arid northern Ethiopia for the last centuries. However, soil and water conservation (SWC) structures have been implemented for a long time to curb soil erosion. Though, like most of the affected areas worldwide, density and distribution of gullies and SWC structures, their causes and interrelations are poorly understood. The aims of this study were to develop a technique for mapping these densities of gullies and SWC structures, to explain their spatial distribution and to analyze changes over the period 1935–2014. Aerial photographs from 1935 to 1936 and Google Earth images from 2014 of the 5142 km2 Geba catchment were used. Transect lines were established to count gullies and SWC structures in order to calculate densities. On average, a gully density of 1.14 km km−2 was measured in 1935–1936 of which the larger portion (75%) were vegetated, indicating they were not very active. Over 80 years, gully density has significantly increased to 1.59 km km−2 with less vegetation growing in their channel, but 66% of these gullies were treated with check dams. There was c. 3 km km−2 of indigenous SWC structures (daget or lynchets) in 1935–1936 whereas a high density (20 km km−2) of introduced SWC structures (mainly stone bunds and terraces) were observed in 2014. The density of gullies is positively correlated with slope gradient and shrubland cover and negatively with cropland cover, whereas the density of SWC structures significantly increased with increasing cropland cover. Density maps of gullies and SWC structures indicate sensitive areas to gully formation and priority areas for the implementation of SWC structures in Geba catchment. The obtained results illustrate the feasibility of the methods applied to map the density of gullies and SWC structures in mountainous areas. Copyright © 2018 John Wiley &amp; Sons, Ltd.

Effect of soil and water conservation on rehabilitation of degraded lands and crop productivity in Maego watershed, North Ethiopia

Many soil and water conservation (SWC) measures were undertaken to decrease land degradation in Ethiopia. However, evaluation of their performance is essential to understand their success or failure and readjusting accordingly in the future planning.  Therefore, the objective of this study was to evaluate effectiveness of SWC measures in rehabilitation of degraded watershed and increase crop productivity in Maego watershed, Ethiopia. Seventy six sample plots were randomly taken from treated and untreated sub-watersheds for woody species and soil sampling. Crops yield was measured on top side, middle zone and below side of SWC structures. There were significantly higher woody species density and diversity, total nitrogen (TN), soil organic matter (SOM) and soil moisture in the treated uncultivated land than the untreated one. The highest tree and sapling species density and diversity, TN and SOM were recorded on the exclosure part of the treated sub-watershed. Landscape position affected soil fertility, but has no effect on woody species density and diversity. The highest barley and wheat yield was measured on top side of SWC structures. Therefore, physical SWC structures should be integrated with exclosure to enhance rehabilitation of degraded watersheds/landscapes. Integration of biological SWC measures that improve soil fertility are essential on the cultivated land of the watershed. Most of the existing SWC structures, especially the old ones are filled with accumulated sediment, so maintenance is needed.

Benefits, limitations and sustainability of soil and water conservation structures in Omo-Gibe basin, Southwest Ethiopia

Different types of soil and water conservation (SWC) structures were introduced to Ethiopia during the last four decades for abating water erosion and sustaining agricultural productivity. This study aimed to determine benefits, limitations and sustainability of SWC structures in the Toni and Bokole watersheds of the Omo Gibe basin. A household survey was conducted on a total of 201 households, which were selected by employing a multistage sampling procedure that covered six rural kebeles.11a smallest local administrative unit. Moreover, six focus group discussions were conducted. The results revealed that more than 80% of respondents in Bokole watershed and all respondents in Toni watershed experienced moderate to severe soil erosion. Farmers were selective in accepting and implementing SWC structures depending on the local land characteristics. Stone bunds were widely implemented in Bokole watershed where rock fragments are abundant and Fanya juu and soil bunds were widely practiced in Toni watershed where rock fragments are not available. Owing to labor intensiveness of the SWC structures, more than 82% of respondents in Bokole and 54% in Toni perceived that labor shortage was a challenge for construction and maintenance. More than 74% of the adopter farmers were also concerned about the loss of cultivable land due to the construction of SWC structures. Number of cattle owned (p < 0.05) and having administrative responsibility in the kebele (p < 0.1) significantly and negatively influenced construction of the SWC structures in Bokole watershed. Runoff overtopping, livestock trampling and cultivation practices were mentioned as the causes of damages for the SWC structures in both watersheds. In Bokole watershed, 92% of the respondents indicated that they repaired the broken SWC structures to sustain their benefits. But 62% of respondents in Toni watershed did not repair. The effort of repairing the SWC structures was significantly (p < 0.05) and negatively influenced by farmland area in Bokole watershed and by education level in Toni watershed. The respondents’ preferences of SWC structures, rate of adoption, willingness to repair and factors affecting adoption and repairing were slightly different in Bokole watershed when compared with Toni watershed. Thus, we concluded that effective implementation and sustainability of SWC structures should critically consider the land users’ socio-economic and environmental intricacy.

Factors influencing the adoption of physical soil and water conservation practices in the Ethiopian highlands

Soil and Water Conservation (SWC) structures have been constructed on cultivated land for nearly 40 years to reduce soil loss and improve crop yields and people's livelihoods in the Ethiopian highlands. However, the success of this huge effort has been mixed, and the main constraints have not been investigated in detail. This study was undertaken to identify the factors determining the adoption of SWC structures in the Ethiopian Highlands. Case study areas were selected from high-potential and low-potential areas. Data were collected from 269 farmers using face-to-face interviews, and through focus group discussions, key informant interviews and field observations. Binary logistic regression model and descriptive statistics were used to analyze the data. The result showed that the majority (87%) of the farmers interviewed were using SWC structures. Regionally, nearly all farmers in the low-potential areas and 56% of farmers in the high-potential areas constructed and were maintaining the structures properly. This disparity is due to the fact that in the low-potential areas there have been strong governmental involvement and technical and financial support, and hence the farmers there have a better understanding of the multiple uses of physical SWC structures than do farmers in the high-potential areas. In addition, off-farm activities and free grazing plays a substantial role. We can conclude that clear understanding of the benefits of SWC structures by farmers, active involvement and technical support from the government, and genuine participation of farmers in SWC practices were found to be main factors in the adoption of SWC measures.

Prediction of soil and water conservation structure impacts on runoff and erosion processes using SWAT model in the northern Ethiopian highlands

PurposeLand degradation due to soil erosion is a serious threat to the highlands of Ethiopia. Various soil and water conservation (SWC) strategies have been in use to tackle soil erosion. However, the effectiveness of SWC measures on runoff dynamics and sediment load in terms of their medium- and short-term effects has not been sufficiently studied.Materials and methodsA study was conducted in 2011 to 2015 in the Gumara-Maksegnit watershed to study the impacts of SWC structures on runoff and soil erosion processes using the soil and water analysis tool (SWAT) model. The study was conducted in two adjacent watersheds where in one of the watersheds, SWC structures were constructed (treated watershed (TW)) in 2011, while the other watershed was a reference watershed without SWC structures (untreated watershed (UW)). For both watersheds, separate SWAT and SWAT-CUP (SWAT calibration and uncertainty procedure) projects were set up for daily runoff and sediment yield. The SWAT-CUP program was applied to optimize the parameters of the SWAT using daily observed runoff and sediment yield data.Results and discussionThe runoff simulations indicated that SWAT can reproduce the hydrological regime for both watersheds. The daily runoff calibration (2011–2013) results for the TW and UW showed good correlation between the predicted and the observed data (R2 = 0.78 for the TW and R2 = 0.77 for the UW). The validation (2014–2015) results also showed good correlation with R2 values of 0.72 and 0.70 for the TW and UW, respectively. However, sediment yield calibration and validation results showed modest correlation between the predicted and observed sediment yields with R2 values of 0.65 and 0.69 for the TW and UW for the calibration and R2 values of 0.55 and 0.65 for the TW and UW for the validation, respectively.ConclusionsThe model results indicated that SWC structures considerably reduced soil loss by as much as 25–38% in the TW. The study demonstrated that SWAT performed well for both watersheds and can be a potential instrument for upscaling and assessing the impact of SWC structures on sediment loads in the highlands of Ethiopia.

Determining RUSLE P‐ and C‐factors for stone bunds and trenches in rangeland and cropland, North Ethiopia

AbstractThe implementation of soil and water conservation (SWC) measures in the Ethiopian Highlands is a top priority to reduce soil erosion rates. However, the effectiveness of these measures for different hillslope gradients and land use conditions remains poorly understood. This study addresses this knowledge gap by determining support practice (P) and cover‐management (C) factors of the Revised Universal Soil Loss Equation for commonly used SWC structures in semi‐arid environments. The factor values were calculated on the basis of soil loss data collected with 21 large runoff plots installed in rangeland and cropland sites. The P‐ and C‐factors were calculated following the recommended procedures. Results show P‐factors ranging from 0.32 to 0.74 for stone bunds, from 0.07 to 0.65 for trenches, and from 0.03 to 0.22 for stone bunds with trenches. Reduced storage capacities due to sediment deposition resulted in significant declines of the effectiveness of SWC structures over time. For example, the average P‐factor value for trenches increased from 0.1 in the first year after installation to 0.51 after 3 years. C‐factor values ranged from 0.23 to 0.82 in rangeland and from 0.03 to 0.35 in cropland. For rangeland, this large variability is due to vegetation cover changes caused by grazing. In cropland, C‐factors vary with crop types and tillage practices. The results of this study not only aid in modelling and quantifying the short‐term impacts of SWC structures on soil erosion rates but also highlight the importance of considering temporal variations of the effectiveness of SWC measures.

Evaluation of Land Use Types and Physical Soil and Water Conservation Structures in Wyebla Watershed, Northwest Ethiopia

The study was carried out in the Wyebla watershed Goncha Siso Enesie Woreda, Northwestern Ethiopia. Similar to the other highland areas in the country Wyebla watershed is characterized, by severe soil erosion and acute water scarcity problems. Hence, the objective of the current investigation was to evaluate different land use types, and physical soil and water conservation (SWC) practices in Wyebla Watershed, Northwest Ethiopia. To check whether the current land use types match with treatment oriented capability classification (TOCC), a transect walk was conducted and measurements were taken during field survey. Rating fitness of recommended versus existing physical SWC structures were given based on TOC classification scheme. Data were analyzed using statistical methods like percentage, mean, frequency, and correlation. From results of TOCC scheme, it can be seen that current land use practices matches with recommended land use types with 83.33% on average. But with regard to rating fitness of existing SWC practices only 36.8% match with the recommended SWC measures.