Your search found 85 records
1 Schmitter, Petra; Zwart, S. J.; Danvi, A.; Gbaguidi, F. 2015. Contributions of lateral flow and groundwater to the spatio-temporal variation of irrigated rice yields and water productivity in a West-African inland valley. Agricultural Water Management, 152:286-298. [doi: https://doi.org/10.1016/j.agwat.2015.01.014]
Groundwater ; Water table ; Flow discharge ; Spatial distribution ; Irrigation ; Rice ; Water productivity ; Water resources ; Water management ; Water balance ; Inland waters ; Valleys ; Crop performance ; Fertilizer application ; Soil organic matter / West Africa
(Location: IWMI HQ Call no: e-copy only Record No: H046882)
Water management techniques to elevate rice yields and productive use of water resources in Africa, frequently lack a substantial spatial assessment as they are often based on plot level measurements without taking into account toposequential effects present in the landscape. These effects have been shown to significantly affect spatio-temporal variations in water availability and rice productivity in Asia. Therefore, this study addresses the spatio-temporal variations of the various water components within irrigated toposequences in an African inland valley and assesses its effect on water productivity and respective rice yields for two irrigation practices: (i) continuous flooding (CF), a well-known water management practice in rice cultivation used worldwide and (ii) a reduced irrigation scheme (RI) where irrigation is applied every 5 days resulting in a 1–2 cm water layer after irrigation. The lateral flow observed in the inland valley had a strong two-dimensional character, contributing to water gains between fields, located at the same toposequential level as well as along toposequences. The toposequential effect on sub-surface hydrological processes masked the overall effect of water management treatment on rice production. Additionally, the associated water productivity (WP) was not found to differ significantly between the treatments when standard calculations (i.e. net irrigation and evapotranspiration) were used but a clear toposequential effect was found for the fertilized lower lying fields when the net irrigation was corrected by the lateral flow component. Results of the established mixed regression model indicated that based on the groundwater table, rainfall and standard soil physico-chemical characteristics rice yields can be predicted in these African inland valleys under continuous flooding and reduced irrigation practices. Validation of the established regression function of inland valleys, representing various groundwater tables in the region, could lead to improved regression functions suitable to estimate spatial variation in rice production and water consumption across scales as affected by water management, fertilizer application and groundwater tables.
2 Meshgi, A.; Schmitter, Petra; Chui, T. F. M.; Babovic, V. 2015. Development of a modular streamflow model to quantify runoff contributions from different land uses in tropical urban environments using Genetic Programming. Journal of Hydrology, 525:711-723. [doi: https://doi.org/10.1016/j.jhydrol.2015.04.032]
Urbanization ; Hydrology ; Stream flow ; Models ; Rainfall runoff relationships ; Land use ; Infiltration ; Catchment areas ; Vegetation / Singapore / Kent Ridge Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H046995)
(2.55 MB)
The decrease of pervious areas during urbanization has severely altered the hydrological cycle, diminishing infiltration and therefore sub-surface flows during rainfall events, and further increasing peak discharges in urban drainage infrastructure. Designing appropriate waster sensitive infrastructure that reduces peak discharges requires a better understanding of land use specific contributions towards surface and sub-surface processes. However, to date, such understanding in tropical urban environments is still limited. On the other hand, the rainfall–runoff process in tropical urban systems experiences a high degree of non-linearity and heterogeneity. Therefore, this study used Genetic Programming to establish a physically interpretable modular model consisting of two sub-models: (i) a baseflow module and (ii) a quick flow module to simulate the two hydrograph flow components. The relationship between the input variables in the model (i.e. meteorological data and catchment initial conditions) and its overall structure can be explained in terms of catchment hydrological processes. Therefore, the model is a partial greying of what is often a black-box approach in catchment modelling. The model was further generalized to the sub-catchments of the main catchment, extending the potential for more widespread applications. Subsequently, this study used the modular model to predict both flow components of events as well as time series, and applied optimization techniques to estimate the contributions of various land uses (i.e. impervious, steep grassland, grassland on mild slope, mixed grasses and trees and relatively natural vegetation) towards baseflow and quickflow in tropical urban systems. The sub-catchment containing the highest portion of impervious surfaces (40% of the area) contributed the least towards the baseflow (6.3%) while the sub-catchment covered with 87% of relatively natural vegetation contributed the most (34.9%). The results from the quickflow module revealed average runoff coefficients between 0.12 and 0.80 for the various land uses and decreased from impervious (0.80), grass on steep slopes (0.56), grass on mild slopes (0.48), mixed grasses and trees (0.42) to relatively natural vegetation (0.12). The established modular model, reflecting the driving hydrological processes, enables the quantification of land use specific contributions towards the baseflow and quickflow components. This quantification facilitates the integration of water sensitive urban infrastructure for the sustainable development of water in tropical megacities.
3 Yilak, D. L.; Tilahun, S. A.; Schmitter, Petra; Nakawuka, Prossie; Enku, T.; Kassawmar, N. T.; Steenhuis, T. S. 2015. Determining the groundwater potential for agricultural use in Ethiopian Highlands [Abstract only] Paper presented at the 10th Alexander von Humboldt Conference 2015 on Water-Food-Energy River and Society in the Tropics. EGU Topical Conference Series, Addis Ababa, Ethiopia, 18-20 November 2015. 2p.
Agriculture ; Groundwater irrigation ; Groundwater recharge ; Water levels ; Water use ; Highlands ; Irrigation water ; Water levels ; Watersheds ; Sustainability ; Case studies / Ethiopia / Ethiopian Highlands / Robit-Bata watershed / Lake Tana
(Location: IWMI HQ Call no: e-copy only Record No: H047278)
(0.01 MB)
The Ethiopian government has declared the Lake Tana - Beles region to be a growth corridor and irrigation development is one of the priorities. Since the dry season river flow is limited, groundwater has the greatest potential for increasing irrigation in the near future. The main drawback is lack of information on sustainable groundwater use and specifically the ground water potential. Therefore the objective of this research is to calculate the annual groundwater recharge. The study was conducted in Robit-Bata, an experimental watershed of 911 ha, located at the south-eastern edge of Lake Tana. Farmers have excavated more than 300 hand dug wells for irrigation use from which, we used 50 wells for water table fluctuation observations for one year starting from April, 2014. Daily Precipitation was recorded for the same period. The annual recharge was estimated using the water – level fluctuation method. Specific yield was defined as the difference of porosity and field capacity of the subsurface formation. The annual average areal groundwater recharge was 640 mm/year, which is 41% of the rainfall and ranged from 50mm to 390mm per week for the various locations in the watershed. The greatest recharge amounts were found in the plains at the foot of the hills and river course areas consisting mostly weathered basalt rock. At those locations the groundwater rose steadily during the rainy monsoon phase. Smaller amount of recharge occurred both near the top of the hills with tough rock formation and in the, flat areas near to stream with sandy and clay deposits and groundwater at, shallow well depth. Our study indicates that the current use of the groundwater seems sustainable. Further research is required for optimized utilization of the limited groundwater resources for irrigation development to meet the food security of the community.
4 Yilak, D. L.; Tilahun, S. A.; Schmitter, Petra; Nakawuka, Prossie; Haile, Alemseged Tamiru; Kassawmar, N. T.; Guzman, C. D.; Steenhuis, T. S. 2015. Adaptation of the SCS [Soil Conservation Service] runoff equation for a (Sub) humid monsoon climate. Paper presented at the 3rd OpenWater Symposium, Addis Ababa, Ethiopia, 16-17 September 2015. 19p.
Climate change ; Monsoon climate ; Humid climate ; Runoff ; Adaptation ; Soil conservation ; Soil moisture ; Watersheds ; Water shortage ; Water balance ; Hydrology ; Models ; Highlands ; River basins ; Rain ; Runoff / Ethiopia / Ethiopian Highland / Maybar Watershed / Anjeni Watershed / Blue Nile Basin
(Location: IWMI HQ Call no: e-copy only Record No: H047279)
(0.01 MB)
The Soil Conservation Service Runoff equation was developed and tested for the temperate climate in the United States. Application to the monsoon climates has been only partially successful. The objective to adapt the SCS equation to a monsoon climate equation is to predict watershed runoff. The adaptation is based on the fact that in many humid areas the main mechanism for direct runoff is saturation excess and in monsoon climates the contributing area expands as a function of the cumulative effective rainfall ( Pe). This then translate in smaller watershed storage (S) in the equation. When estimating runoff contributing area within a watershed and assessing the runoff mechanisms, we have used the original concept of SCS-CN approach in a 113 ha Anjeni and 113ha Maybar Watersheds in the headwaters of the Blue Nile Basin, North Ethiopian highland. Analysis was done at daily, weekly and biweekly base using nine years of hydrological data (1988-97) by classifying the rainfall seasons in to six based on the seasonal cumulative of effective rainfall (Pe). The initial abstraction (Ia) was taken to be equal to the evapotranspiration loss (E) computed by Thornthwaite-Mather water balance method in replacement of the 20% of the potential storage (S). Effective rainfall (Pe) is the difference of total rainfall and Ia. The model performed more as the seasonal cumulative Pe is increased indicating that runoff responses occurred as the watershed saturated. The proportion of runoff contributing area (Af) increased linearly until the cumulative Pe up to nearly 500mm and then the watershed reaches in equilibrium for addition increase of Pe, which is in line with the concept of partial source area hydrology.
5 Yiak, D. L.; Tilahun, S. A.; Schmitter, Petra; Nakawuka, Prossie; Steenhuis, T. S. 2015. Groundwater recharge of Robit - Bata Experimental Watershed, Lake Tana Basin, Ethiopia [Abstract only] Paper presented at the 3rd International Conference on the Advancements of Science and Technology [ICAST], Bahir Dar, Ethiopia, 8-9 May 2015. 1p.
Groundwater recharge ; Groundwater irrigation ; Watersheds ; Water use ; Water table ; River basins ; Rain / Ethiopia / Lake Tana Basin / Robit - Bata Experimental Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H047313)
(0.04 MB)
Irrigation development is a policy priority for the Laka Tana basin. However available baseflow can irrigate less than 3% of area. The irrigated area can be increased from water stored in constructed reservoirs, pumping water from Lake Tana and by using groundwater. While groundwater has the greatest potential for increasing irrigation in the near future, the main drawback is a lack of information on sustainable groundwater use and specifically the ground water recharge. Therefore the objective of this research is to calculate the annual recharge to the ground water. The study is conducted in Robit-Bata, an experimental watershed of 911 ha, located at the south-eastern edge of Lake Tana. Farmers have excavated more than 300 hand dug wells for irrigation and we used 50 shallow groundwater wells and observed water table fluctuation and precipitation for the past one year. The annual recharge was estimated using water – level fluctuation method. Specific yield was taken to be the difference of porosity and field capacity of the subsurface formation. The annual average areal groundwater recharge of the watershed was 200 mm/year, which is 12% of the rainfall and ranged from 80mm to 500mm for the various locations in the watershed. The greatest recharge amounts were found at the foot of the hillside in river course plane areas consisting mostly weathered basalt rock. Here the groundwater was up to 15 m deep and rose steadily during the rainy monsoon phase. Smaller amount of recharge occurred both near the top of the hills with tough rock formation and in the, flat areas near to stream sandy and clay deposits and groundwater at, shallow well depth. Our study indicates that the current use of the groundwater is sustainable, but will become unsustainable if many more wells are constructed. Sufficiency and sustainable use of the shallow groundwater needs further research.
6 Addisie, M. B.; Ayele, G. K.; Gessesse, A. A.; Tilahun, S. A.; Zegeye, A. D.; Moges, M.; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2015. Reducing surface and subsurface water flow effect on gullies through low cost measures [Abstract only] Paper presented at the 10th Alexander von Humboldt Conference 2015 on Water-Food-Energy River and Society in the Tropics. EGU Topical Conference Series, Addis Ababa, Ethiopia, 18-20 November 2015. 1p.
Surface water ; Groundwater ; Flow discharge ; Gully erosion ; Erosion control ; Watersheds ; Water table ; Cost analysis ; Soil properties ; Case studies / Ethiopia / Amhara State / Birr Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H047331)
(0.04 MB)
Gully erosion in the humid Ethiopian highlands intensified in recent decades. The study was conducted in the Birr watershed located south west of Bahir Dar the capital of Amhara regional state, Ethiopia. We studied 14 gullies having similar morphology at three sub watersheds. The watershed covers a total area of 414 ha. The monitoring continued over the 2013 to 2014 monsoon season to better understand the factors controlling gully erosion and the effectiveness of erosion control structures. Perched ground water table was measured at the gully heads and erosion pins were installed to monitor the rate of recession from uncontrolled heads. Though soil properties, ground cover, gully morphology had small contribution for the gully development; water fall effect at the head of the gully and elevated water table depth at both heads and banks played the key role. Therefore the study focused on reducing the water fall and elevated water table effect by applying two low cost gully control approaches. The first approach was regrading the gully heads and banks at 45o and the second approach follows regrading the gully heads at 45o and putting a graded type of stone rip rap. Large stones were anchored at the toe of the head maintaining the stable gully bed slope. The result shows that unprotected gully heads retreat an average of 4m which is equivalent to 37m3 volume of soil loss. The maximum and minimum head cut retreat was between 0 and 22.5m. The total area damaged by annual gully head retreat was 240m2 and total volume of soil lost was 444m3. The treated gully heads did not show any retreat during the monitoring period. Compared with simple reshaping of gully heads, integration with Stone rip rap was an effective and low cost measure in the study watershed. Plantation could not stop the upslope migration of heads though it had the potential to trap sediments down slope. Heads with stone rip rap allows fast re vegetation whereas unprotected reshaped heads and banks took longer time to re vegetate and stabilized. Time of reshaping was important for the stability of banks and heads.
7 Schmitter, Petra; Goedbloed, A.; Galelli, S.; Babovic, V. 2016. Effect of catchment-scale green roof deployment on stormwater generation and reuse in a tropical city. Journal of Water Resources Planning and Management, 142(7):1-13. [doi: https://doi.org/10.1061/(ASCE)WR.1943-5452.0000643]
Catchment areas ; Drainage ; Precipitation ; Water reuse ; Water management ; Vegetation ; Hydrological cycle ; Hydraulic conductivity ; Models ; Reservoir operation ; Urbanization ; Discharges ; Rainfall-runoff relationships ; Weather / Singapore / Marina Reservoir
(Location: IWMI HQ Call no: e-copy only Record No: H047458)
(12.37 MB)
Low-impact development (LID) comprises a broad spectrum of stormwater management technologies for mitigating the impacts of urbanization on hydrological processes. Among these technologies, green roofs are one of the most adopted solutions, especially in densely populated metropolitan areas, where roofs take up a significant portion of the impervious surfaces and land areas are scarce. While the in situ hydrological performance of green roofs—i.e., reduction of runoff volume and peak discharge—is well addressed in literature, less is known about their impact on stormwater management and reuse activities at a catchment or city scale. This study developed an integrated urban water cycle model (IUWCM) to quantitatively assess the effect of uniform green roof deployment (i.e., 25, 50, and 100% conversion of traditional roofs) over the period 2009–2011 in the Marina Reservoir catchment, a 100-km2, highly urbanized area located in the heart of Singapore. The IUWCM consists of two components: (1) a physically based model for extensive green roofs integrated within a one-dimensional numerical hydrological-hydraulic catchment model linked with (2) an optimization-based model describing the operation of the downstream, stormwater-fed reservoir. The event-based hydrological performance of green roofs varied significantly throughout the simulation period with a median of about 5% and 12% for the catchment scale reduction of runoff volume and peak discharge (100% conversion of traditional roofs). The high variability and lower performance (with respect to temperate climates) are strongly related to the tropical weather and climatic conditions—e.g., antecedent dry weather period and maximum rainfall intensity. Average annual volume reductions were 0.6, 1.2, and 2.4% for the 25, 50, and 100% green roof scenarios, respectively. The reduction of the stormwater generated at the catchment level through green roof implementation had a positive impact on flood protection along Marina Reservoir shores and the energy costs encountered when operating the reservoir. Vice versa, the drinking water supply, which depends on the amount of available stormwater, decreased due to the evapotranspiration losses from green roofs. Better performance in terms of stormwater reuse could only be obtained by increasing the time of concentration of the catchment. This may be achieved through the combination of green roofs with other LID structures.
8 Schmitter, Petra; Haileslassie, Amare; Nakawuka, Prossie; Gebregziabher, Gebrehaweria; Tesema, M.; Tegegne, D.; Abdela, M.; Yilak, D. L.; Tilahun, S.; Ayana, M.; Langan, Simon. 2016. The importance of Ethiopian soils in irrigation and overall watershed management [Abstract only] Paper presented at the Strategic Forum on Sustainable development in Africa: Opportunities and Pitfalls for Universities and NGO’s, Heverlee, Belgium, 15 January 2016. 1p.
Watershed management ; Irrigation methods ; Surface irrigation ; Groundwater irrigation ; Irrigation water ; Water quality ; Water management ; Soil sampling ; Soil moisture ; Agronomic practices ; Crop production ; Tillage / Ethiopia
(Location: IWMI HQ Call no: e-copy only Record No: H047383)
(0.01 MB)
Irrigation has a large potential to increase agricultural output and yield per unit area. However, the long term sustainability increased production, together with degradation of the soils (and associated water bodies) in irrigated areas may be irreparably damaged by inappropriate watering schedules. In Ethiopia, surface and groundwater irrigation has been promoted intensively throughout the country. While many projects focus on individual or scheme level water access, very little is known about the sustainability of irrigation in Ethiopia. Aside, from water quantity the quality of irrigation water has a significant impact on soil stability and its chemical properties. In the Ziway, a very important irrigation area in Oromia, soils are increasingly becoming sodic due to the large irrigation quantities and the poor water quality. The International Water Management Institute focusses through various research for development projects on improving irrigation water management, increasing groundwater recharge and assessing the environmental impact of irrigation for various soils throughout the Amhara, Oromia and SNNPR region. Irrigation scheduling tools have been introduced at individual and scheme based small holder farms for the irrigation of high value horticultural and fodder crops to improve water and crop productivity and reduce nutrient leaching. Simultaneously groundwater recharge experiments were carried out using deep tillage and soil & water conservation practices in the rainy season. In these studies, soils are sampled, irrigation quantified, soil moisture measured and standard agronomic practices monitored. Additionally, socio-economic data are being collected on household composition, land holding, labor involved in as well as income generated by the various technologies. Preliminary results showed that crop productivity was not effect while reducing water between 18-35% as function of the prevailing soil types. For the groundwater recharge studies lowest runoff values and highest crop productivity values were observed in the deep tillage plots compared to zero and normal tillage. The socio-economic as well as biophysical data are used in field as well as watershed models to assess the environmental and economic impact of various irrigation scenarios throughout the agro-ecological zones.
9 Addisie, M. B.; Ayele, G. K.; Gessess, A. A.; Tilahun, S. A.; Zegeye, A. D.; Moges, M. M. [NARS]; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2015. Hydrological and morphological factors at gully heads in the humid northern Ethiopian Highlands, Birr watershed [Abstract only] In Nyssen J., Enyew A., Poesen J et al. (Eds.). International Conference on Tropical Lakes in a Changing Environment: Water, Land, Biology, Climate and Humans (TropiLakes), Bahir Dar, Ethiopia, 23-29 September 2015. Book of Abstracts. Bahir Dar, Ethiopia: Bahir Dar University. pp.72.
Hydrological factors ; Gully erosion ; Humid climate ; Water table ; Watersheds ; Highlands ; Soils / Ethiopia / Birr Watershed / Ethiopian Highlands
(Location: IWMI HQ Call no: e-copy only Record No: H047416)
(0.10 MB)
In the Ethiopian highlands, gully erosion is severe. Although attempts to prevent gullying, it remains a challenge. Our objectives are to understand better the processes that control gully head cut retreat. The study was conducted in Birr watershed located at South West of Bahir Dar, Ethiopia. Twelve gully heads were selected and monitored from July to October, 2014. We measured gully head morphology, length of recession via pegging technique, soil analysis to determine soil shear strength, physical and chemical properties, water table elevations and catchment physical characteristics. Two active gully head cuts were arrested with stone riprap after regarding at 450. The result shows that the maximum rate of head cut retreat was between 0 to 22.5m. There was no head retreat observed from the protected heads compared with unprotected heads. The average short term head cut retreat was much greater than that observed in semiarid highlands of northern Ethiopia. The greater gulley rate of recession in the humid monsoon climate is likely caused by the water table that was above the gully bottom. In August when the soil became saturated, about 45% of head cut migration occurred. Thus the water table contributed to the slumping of gully heads and weakened the strength of the soil cohesion. The soil shear strength test result shows, angle of internal friction was by far greater than the slope of gully heads where heads are located in the periodically saturated flat lands. The width depth ratio showed that the shallow depth heads were controlled by fluvial erosion whereas for the deep gully heads both fluvial and mass wasting due to tension cracks was the main driving force. Both the water table control and protecting the head cuts of shallow gullies plays a key role in reducing the sediment contribution of gully in the humid Ethiopian highlands.
10 Slaets, J. I. F.; Schmitter, Petra; Hilger, T.; Vien, T. D.; Cadisch, G. 2016. Sediment trap efficiency of paddy fields at the watershed scale in a mountainous catchment in northwest Vietnam. Biogeosciences, 13:3267-3281. [doi: https://doi.org/10.5194/bg-13-3267-2016]
Sedimentation ; Paddy fields ; Watersheds ; Highlands ; Catchment areas ; Cropping systems ; Agriculture ; Maize ; Rice ; Irrigation water ; Soil fertility ; Erosion ; Reservoir storage ; Rain / southeast Asia / Vietnam
(Location: IWMI HQ Call no: e-copy only Record No: H047584)
http://www.biogeosciences.net/13/3267/2016/bg-13-3267-2016.pdf
https://vlibrary.iwmi.org/pdf/H047584.pdf
https://vlibrary.iwmi.org/pdf/H047584.pdf
(1.33 MB)
Composite agricultural systems with permanent maize cultivation in the uplands and irrigated rice in the valleys are very common in mountainous southeast Asia. The soil loss and fertility decline of the upland fields is well documented, but little is known about reallocation of these sediments within the landscape. In this study, a turbidity-based linear mixed model was used to quantify sediment inputs, from surface reservoir irrigation water and from direct overland flow, into a paddy area of 13 ha. Simultaneously, the sediment load exported from the rice fields was determined. Mid-infrared spectroscopy was applied to analyze sediment particle size. Our results showed that per year, 64Mgha-1 of sediments were imported into paddy fields, of which around 75% were delivered by irrigation water and the remainder by direct overland flow during rainfall events. Overland flow contributed one-third of the received sandy fraction, while irrigated sediments were predominantly silty. Overall, rice fields were a net sink for sediments, trapping 28Mgha-1 a-1 or almost half of total sediment inputs. As paddy outflow consisted almost exclusively of silt- and clay-sized material, 24Mgha-1 a-1 of the trapped amount of sediment was estimated to be sandy. Under continued intensive upland maize cultivation, such a sustained input of coarse material could jeopardize paddy soil fertility, puddling capacity and ultimately food security of the inhabitants of these mountainous areas. Preventing direct overland flow from entering the paddy fields, however, could reduce sand inputs by up to 34 %.
11 Agide, Z.; Haileslassie, Amare; Sally, H.; Erkossa, Teklu; Schmitter, Petra; Langan, Simon; Hoekstra, D. 2016. Analysis of water delivery performance of smallholder irrigation schemes in Ethiopia: diversity and lessons across schemes, typologies and reaches. Nairobi, Kenya: International Livestock Research Institute (ILRI). 38p. (Livestock and Irrigation Value Chains for Ethiopian Smallholders (LIVES) Working Paper 15)
Irrigation schemes ; Irrigation systems ; Irrigated land ; Smallholders ; Performance evaluation ; Performance indexes ; Water supply ; Water delivery ; Water distribution ; Water levels ; Water demand ; Sustainability ; Equity ; Cropping systems / Ethiopia
(Location: IWMI HQ Call no: e-copy only Record No: H047586)
(1.36 MB)
12 Slaets, J. I. F.; Schmitter, Petra; Hilger, T.; Hue, D. T. T.; Piepho, H. P.; Vien, T. D.; Cadisch, G. 2016. Sediment-associated organic carbon and nitrogen inputs from erosion and irrigation to rice fields in a mountainous watershed in Northwest Vietnam. Biogeochemistry, 129(1):93-113. [doi: https://doi.org/10.1007/s10533-016-0221-9]
Sedimentation ; Soil fertility ; Organic fertilizers ; Carbon ; Organic nitrogen compounds ; Nitrogen fertilizers ; Erosion ; Irrigation water ; Rice fields ; Maize ; Highlands ; Watersheds ; Nutrient balance ; Landscape ; Reservoirs ; Land use ; Runoff ; Shifting cultivation ; Surface water ; Water quality / Vietnam
(Location: IWMI HQ Call no: e-copy only Record No: H047588)
(1.27 MB)
Maintaining indigenous nutrient supply and positive nutrient balances are key factors in sustaining rice yields. Irrigation systems act as conveyers for water, sediments and nutrients throughout landscapes, especially in mountainous, cultivated tropical areas where erosivity is usually high. Contributions of erosion and irrigation to the nutrient balance of paddy fields, however, are rarely assessed. In this study, a turbidity-based method was used to quantify sediment-associated organic carbon and nitrogen as well as dissolved nitrogen inputs from erosion and irrigation to a 13 ha rice area in Northwest Vietnam. The irrigation source is a surface reservoir, and both reservoir and irrigation channel are surrounded by permanent upland maize cultivation on the steep slopes. Additionally, organic carbon and nitrogen loads in paddy outflow were determined to obtain nutrient budgets. Irrigation contributed 90 % of sediment-associated organic carbon inputs and virtually all nitrogen inputs. Analysis of ammonium and nitrate in total nitrogen loads showed that 24 % of the total N inputs from irrigation to the rice area, or 0.28 Mg ha-1 a-1, were plant-available. Loads measured at the outlet of rice fields showed that paddies were a trap for sediment-associated nutrients: balancing inputs and outflow, a net load of 1.09 Mg ha-1 a-1 of sediment-associated organic carbon and 0.68 Mg ha-1 a-1 of sediment-associated nitrogen remained in the rice fields. Sediment-associated organic carbon and nitrogen inputs thus form an important contribution to the indigenous nutrient supply of rice in these maize-paddy systems, while the rice fields simultaneously capture nutrients, protecting downstream areas from the effects of land use intensification on surrounding slopes. These results underscore the importance of upland-lowland linkages in tropical, mountainous, erosion-prone areas.
13 Tesema, M.; Schmitter, Petra; Nakawuka, Prossie; Tilahun, S. A.; Steenhuis, T.; Langan, Simon. 2016. Evaluating irrigation technologies to improve crop and water productivity of onion in Dangishta watershed during the dry monsoon phase. Paper presented at the International Conference of the Advancement of Science and Technology, Bahir Dar, Ethiopia, 17-18 July 2016. 10p.
Crop production ; Crop management ; Water productivity ; Water use efficiency ; Water conservation ; Water management ; Onions ; Monsoon climate ; Dry season ; Watershed services ; Wet cultivation ; Soil moisture ; Soil water balance ; Rhizosphere ; Rain ; Agriculture ; Fertilizer application / Ethiopia / Dangishta Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H047635)
(611 KB)
14 Addisie, M. B.; Ayele, G. K.; Gessesse, A. A.; Tilahun, S. A.; Moges, M. M.; Zegeye, A. D.; Mekuria, Wolde; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2016. Rehabilitating gullies with low cost methods, in the sub humid Ethiopian highlands. Paper presented at the International Conference of the Advancement of Science and Technology, Bahir Dar, Ethiopia, 17-18 July 2016. 10p.
Gully erosion ; Humid zones ; Highlands ; Environmental degradation ; Ecosystems ; Watersheds ; Riverbank protection ; Vegetation ; Plantations ; Sedimentation
(Location: IWMI HQ Call no: e-copy only Record No: H047636)
(691 KB)
Gully erosion in the highlands of Ethiopia has reduced agricultural productivity and degraded ecosystem services. To better understand the processes controlling gully erosion and design effective control measures, a study was conducted in the headwaters of the Birr watershed for three consecutive years (2013-2015). Fourteen gullies with similar morphology were studied in three adjacent sub-watersheds. Stabilization measures were applied to 5 of the 14 gully heads. Three gully control measures were compared: a) reshaping gully banks and head to a 45 degree slope with stone rip rap on the gully heads, b) controlling gully bed grade, and c) planting grasses and trees on shallow gullies (i.e., < 3 m deep). Results demonstrated that gully control measures were effective in controlling the expansion of gullies as no further retreat was observed for the 5 treated gully heads, whereas the average retreat was 3 meters with a maximum of 22.5 m for the 9 untreated gullies. The migration of untreated gully heads produced an average soil loss of 38 tons per gully. Compared with simple reshaping of gully heads, the additional integration with stone rip rap was an effective and low cost measure. Vegetative treatment by itself could not stop the upslope migration of gully heads, though it had the potential to trap sediments. Re-vegetation at gully heads stabilized with stone rip rap occurred faster than at unprotected, reshaped heads and banks. From the fourteen rehabilitation treatments, gully head protection integrated with plantation showed the largest potential in decreasing gully development in terms of labor, time and material it requires.
15 Haileslassie, Amare; Agide, Z.; Erkossa, Teklu; Hoekstra, D.; Schmitter, Petra. 2016. On-farm smallholder irrigation performance in Ethiopia: from water use efficiency to equity and sustainability. Nairobi, Kenya: International Livestock Research Institute (ILRI). 33p. (Livestock and Irrigation Value Chains for Ethiopian Smallholders (LIVES) Working Paper 19)
Irrigation schemes ; Irrigation water ; Irrigated farming ; Water productivity ; Water supply ; Water use efficiency ; Smallholders ; Equity ; Sustainability ; Land productivity ; Crop production ; Vegetables ; Cereals ; Maize ; Performance indexes / Ethiopia
(Location: IWMI HQ Call no: e-copy only Record No: H047710)
https://cgspace.cgiar.org/bitstream/handle/10568/77017/LIVES_wp_19.pdf?sequence=1
https://vlibrary.iwmi.org/pdf/H047710.pdf
https://vlibrary.iwmi.org/pdf/H047710.pdf
(811 KB)
The performance of smallholder irrigation schemes are challenged by several factors: among which water insecurity and low land and water productivity are the main ones. This paper evaluates the on-farm management of nine smallholder irrigation schemes from four regional states in Ethiopia. The schemes are diverse in several aspects and we clustered them into three typologies: Modern, semi-modern and traditional. Indicators such as land productivity (LP), crop water productivity (CWP) were used in evaluating performances. Data input to the target indicators was collected through household survey, field observation, measurements (canal water flow monitoring), literature review and focus group discussion (FGD). The result illustrates apparent variability of LP among schemes; scheme typology and reaches. The lowest value of LP was estimated for the traditional schemes and inter-scheme variation was also notable. For example for onion, the value for LP ranged between 7.13 and 14.55 tonnes/ha. For tomato the range was even wider: 0.9–10.29 tonnes/ha. Meki scheme showed the highest land productivity for onion and tomato with the magnitude of 14.55 and 10.29 tonnes/ha respectively. For irrigated cereals (maize and wheat) LP values showed a similar trend as for vegetables. For example the LP value for maize range between 0.65 and 3.92 tonnes/ha and for wheat the range was narrower (0.6 and 1.56 tonnes/ha). Generally these values are less than the values reported as sub-Saharan Africa (SSA) regional average suggesting the need to address yield limiting factors in smallholder schemes in Ethiopia. Water productivity by water supplied at field levels (WPf) for cereals was generally on the lower side; it is somewhat on the higher side for vegetables compared to observations from SSA. Schemes and reaches with higher land productivity do not necessarily shows higher WPf. Modern schemes and head irrigators have usually higher land productivity but low water productivity. The opposite holds true for the traditional irrigation and tail irrigators. The traditional schemes and tail irrigator normally suffer from water shortage and most often practicing forced deficit irrigation and also select crops with low water requirement. Hence they save water while trying to minimize impact on the yield through crop selection. Implicitly future direction of improving smallholder irrigation need to acknowledge this reality and put efforts to save water on head irrigators and increase land productivity under traditional and tail irrigators and promote sustainability and equitable share of water in smallholder irrigation. Probably alternatives such as valuation of water and a consumption-based water charge need to be taken into account in efforts to discourage over irrigation and enhance equitable water management by smallholders. It is also important to note that smallholder water management decisions are complex and so are the values for their performance indicators. Therefore, any development efforts dealing with smallholder irrigation need to disentangle and understand this diversity and ensure interventions are context specific.
16 Moges, M. A.; Schmitter, Petra; Tilahun, S. A.; Langan, Simon; Dagnew, D. C.; Akale, A. T.; Steenhuis, T. S. 2017. Suitability of watershed models to predict distributed hydrologic response in the Awramba Watershed in Lake Tana Basin. Land Degradation and Development, 28(4):1386-1397. [doi: https://doi.org/10.1002/ldr.2608]
Watershed management ; Hydrology ; Catchment areas ; Models ; Land degradation ; River basin management ; Spatial distribution ; Rainfall-runoff relationships ; Infiltration water ; Wet season ; Calibration ; Groundwater ; Water table ; Water levels / Ethiopia / Lake Tana River Basin / Awramba Watershed
(Location: IWMI HQ Call no: e-copy only Record No: H047780)
Planning effective landscape interventions is an important tool to fight against land degradation and requires knowledge on spatial distribution of runoff. The objective of this paper was to test models that predict temporal and spatial distribution of runoff. The selected models were PED-WM, HBV-IHMS and SWAT. We choose 7 km2 Awramba watershed in the Lake Tana basin with detailed hydrological information for testing these models. Discharge at the outlet, rainfall and distributed information on infiltration rates, water table and extent of the saturated area were collected from 2013 to 2015. The maximum saturated area was 6.5% of the watershed. Infiltration rates exceeded rainfall intensities 91% of the time. Hence saturation excess runoff was the main runoff mechanism. Models were calibrated for the rainy seasons 2013, 2014 and validated for 2015. For daily flow validation, the PED-WM model (Nash Sutcliff efficiency, NSE = 0.61) outperformed HBV-IHMS (NSE = 0.51) and SWAT (NSE = 0.48). Performance on monthly time step was similar. Difference in model behavior depended on runoff mechanism. In PED-WM saturation excess is the main direct runoff process and could predict the maximum extent of the saturated area closely at 6.9%. HBV-IHMS model runoff simulation depended on soil moisture status and evapotranspiration, and hence was able to simulate saturation excess flow but not the extent of the saturated area. In SWAT where infiltration excess is the main runoff mechanism could only predict the monthly discharges well. This study shows that prevailing runoff mechanisms and distribution of runoff source areas should be used for proper model selection.
17 Schmitter, Petra; Haileslassie, Amare; Desalegn, Y.; Tilahun, S.; Langan, Simon; Barron, Jennie. 2016. Improving on-farm water management by introducing wetting front detectors to small scale irrigators in Ethiopia [Abstract only] Paper presented at the Annual Tropical and Subtropical Agricultural and Natural Resource Management (Tropentag) Conference on Solidarity in a Competing World - Fair Use of Resources, Vienna, Austria, 18-21 September 2016. 1p.
Water management ; Water productivity ; Water distribution ; Water user associations ; Small scale systems ; Irrigation scheduling ; Irrigation equipment ; Wetting front ; Crop production ; Cereal crops ; Vegetables ; Agroecology ; Farmers ; Soil conditioners ; Farm management / Ethiopia
(Location: IWMI HQ Call no: e-copy only Record No: H047872)
Smallholder irrigation to improve food security in the dry season as well as economic and demographic growth within Ethiopia is developing rapidly. However, the long term sustainability of increased irrigated production, together with degradation of soils (and associated water bodies) may be irreparably damaged by inappropriate watering schedules. In irrigation schemes, over-irrigation results in periodic water scarcity issues and in some cases sodicity. The aim of the study was to evaluate whether using wetting front detectors (WFD), a simple mechanical irrigation advice tool, would give farmers the right knowledge on when and how much to irrigate. Therefore, improving sustainable on-farm water management without negatively affecting crop and water productivity while fostering a more equitable water distribution within the scheme. The study, conducted in different regions of Ethiopia, covered various agro-ecological zones and soil conditions with over 200 farmers irrigating cereals or vegetables. Farmers and water user associations were trained on using the WFD to irrigate and distribute water within the scheme. Irrigation and crop performance was evaluated against control plots, having the same crop variety and management but traditional irrigation practices. Reduction in applied irrigation volume due to the WFD differed within and between sites due to furrow length, soil texture and farmer experience. Although yield increases were highly variable between farmers due to differences in farm management and crop variety cultivated, there was a positive effect of WFD on water productivity. Water productivity on average increased by 9 % whereas yields for the different crops increased between 13 and 17 %. In some cases the volume of water saved could double the cropped area. The reduction of irrigation events, when using the WFD, led to labour saving (up to 11 working days per ha) and fuel saving (between 50 and 150 US$ per ha). In both sites, farmers positively evaluated the scheduling tool, acknowledging that they learned to save water without negatively impacting crop productivity. The study showed that by providing access to when and how much to irrigate, farmers can positively adjust their on-farm water management resulting in more sustainable usage of their natural resources.
18 Slaets, J. I. F.; Piepho, H.-P.; Schmitter, Petra; Hilger, T.; Cadisch, G. 2017. Quantifying uncertainty on sediment loads using bootstrap confidence intervals. Hydrology and Earth System Sciences, 21:571-588. [doi: https://doi.org/10.5194/hess-21-571-2017]
Sediment ; Uncertainty ; Pollutants ; Nutrients ; Soil fertility ; Reservoirs ; Watersheds ; Water quality ; Discharges ; Catchment areas ; Rain ; Uncertainty ; Hydrological factors / Vietnam
(Location: IWMI HQ Call no: e-copy only Record No: H047983)
http://www.hydrol-earth-syst-sci.net/21/571/2017/hess-21-571-2017.pdf
https://vlibrary.iwmi.org/pdf/H047983.pdf
https://vlibrary.iwmi.org/pdf/H047983.pdf
(1.04 MB)
Load estimates are more informative than constituent concentrations alone, as they allow quantification of on- and off-site impacts of environmental processes concerning pollutants, nutrients and sediment, such as soil fertility loss, reservoir sedimentation and irrigation channel siltation. While statistical models used to predict constituent concentrations have been developed considerably over the last few years, measures of uncertainty on constituent loads are rarely reported. Loads are the product of two predictions, constituent concentration and discharge, integrated over a time period, which does not make it straightforward to produce a standard error or a confidence interval. In this paper, a linear mixed model is used to estimate sediment concentrations. A bootstrap method is then developed that accounts for the uncertainty in the concentration and discharge predictions, allowing temporal correlation in the constituent data, and can be used when data transformations are required. The method was tested for a small watershed in Northwest Vietnam for the period 2010–2011. The results showed that confidence intervals were asymmetric, with the highest uncertainty in the upper limit, and that a load of 6262 Mg year-1 had a 95 % confidence interval of (4331, 12 267) in 2010 and a load of 5543 Mg an interval of (3593, 8975) in 2011. Additionally, the approach demonstrated that direct estimates from the data were biased downwards compared to bootstrap median estimates. These results imply that constituent loads predicted from regression-type water quality models could frequently be underestimating sediment yields and their environmental impact.
19 Worqlul, A. W.; Jeong, J.; Dile, Y. T.; Osorio, J.; Schmitter, Petra; Gerik, T.; Srinivasan, R.; Clark, N. 2017. Assessing potential land suitable for surface irrigation using groundwater in Ethiopia. Applied Geography, 85:1-13. [doi: https://doi.org/10.1016/j.apgeog.2017.05.010]
Surface irrigation ; Groundwater recharge ; Groundwater irrigation ; Water storage ; Geographical information systems ; Land suitability ; Land use ; Irrigated land ; Agroindustry ; Soil texture ; Slopes ; Rain ; Evapotranspiration ; Water requirements ; Water resources ; Water availability ; River basins ; Population density ; Mapping ; Farmer-led irrigation ; Crops / Ethiopia
(Location: IWMI HQ Call no: e-copy only Record No: H048151)
http://www.sciencedirect.com/science/article/pii/S0143622816306269/pdfft?md5=d81ce4d77a5a37854e1918796d7b3995&pid=1-s2.0-S0143622816306269-main.pdf
https://vlibrary.iwmi.org/pdf/H048151.pdf
https://vlibrary.iwmi.org/pdf/H048151.pdf
(5.35 MB)
Although Ethiopia has abundant land for irrigation, only a fraction of its potential land is being utilized. This study evaluates suitability of lands for irrigation using groundwater in Ethiopia using GIS-based Multi-Criteria Evaluation (MCE) techniques in order to enhance the country's agricultural industry. Key factors that significantly affect irrigation suitability evaluated in this study include physical land features (land use, soil, and slope), climate (rainfall and evapotranspiration), and market access (proximity to roads and access to market). These factors were weighted using a pair-wise comparison matrix, then reclassified and overlaid to identify suitable areas for groundwater irrigation using a 1-km grid. Groundwater data from the British Geological Survey were used to estimate the groundwater potential, which indicates the corresponding irrigation potential for major crops. Results indicated that more than 6 million ha of land are suitable for irrigation in Ethiopia. A large portion of the irrigable land is located in the Abbay, Rift Valley, Omo Ghibe, and Awash River basins. These basins have access to shallow groundwater (i.e., depth of groundwater less than 20 m from the surface) making it easier to extract. The comparison between available groundwater and total crop water requirements indicate that groundwater alone may not be sufficient to supply all suitable land. The study estimates that only 8% of the suitable land can be irrigated with the available shallow groundwater. However, groundwater is a viable option for supplementing surface water resources for irrigation in several basins in the country.
20 Addisie, M. B.; Ayele, G. K.; Gessess, A. A.; Tilahun, S. A.; Zegeye, A. D.; Moges, M. M.; Schmitter, Petra; Langendoen, E. J.; Steenhuis, T. S. 2017. Gully head retreat in the sub-humid Ethiopian Highlands: the Ene-Chilala Catchment. Land Degradation and Development, 28(5):1579-1588. [doi: https://doi.org/10.1002/ldr.2688]
Gully erosion ; Erosion control ; Humid zones ; Highlands ; Catchment areas ; Sedimentation ; Wet season ; Monitoring ; Soil texture / East Africa / Ethiopia / Ene-Chilala Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H048152)
In the northern highlands of Ethiopia, gully erosion is severe. Despite many efforts to implement gully prevention measures, controlling gully erosion remains a challenge. The objective is to better understand the regional gully erosion processes and to prevent gully head retreat. The study was conducted in the Ene-Chilala catchment in the sub-humid headwaters of the Birr River located southwest of Bahir Dar, Ethiopia. Twelve gully heads were monitored during the 2014 and 2015 rainy monsoon phase. We measured gully head morphology and retreat length, soil shear strength, ground water table levels, and catchment physical characteristics. Two active gully head cuts were treated in 2014 and an additional three head cuts in 2015 by regrading their slope to 45° and covering them with stone riprap. These treatments halted the gully head advance. The untreated gullies were actively eroding due to groundwater at shallow depths. The largest head retreat was 22.5 m, of which about half occurred in August of the first year when the surrounding soil was fully saturated. Lowering both the water table and protecting the gully heads can play a key role in reducing gully expansion and soil loss due to gully erosion in the Ethiopian highlands.
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