Your search found 45 records
1 Gurung, Pabitra; Bharati, Luna. 2011. Downstream hydrological impacts of the Melamchi inter-basin water transfer plan. In Nepal. Department of Irrigation. Proceedings of National Irrigation Seminar Micro to Mega: Irrigation for Prosperous Nepal, Kathmandu, Nepal, 13-14 July 2011. Lalitpur, Nepal: Department of Irrigation. pp.161-168.
Downstream ; Hydrological factors ; River basins ; Water availability ; Water transfer ; Water supply ; Drinking water ; Water balance ; Models ; Dry season ; Wet season / Nepal / Melamchi / Kathmandu Valley / Indrawati River
(Location: IWMI HQ Call no: e-copy only Record No: H044590)
(1.33 MB)
2 Gurung, Pabitra; Bharati, Luna. 2012. Downstream impacts of the Melamchi Inter-Basin Water Transfer Plan (MIWTP) under current and future climate change projections. Hydro Nepal: Journal of Water, Energy and Environment, April:23-29. (Special issue on "Proceedings of National Conference on Water, Food Security and Climate Change in Nepal" with contributions by IWMI authors).
Downstream ; River basins ; Drinking water ; Water availability ; Water supply ; Water transfer ; Climate change ; Simulation models ; Wet season ; Dry season ; Crop management ; Water requirements ; Irrigation / Nepal / Kathmandu / Koshi River Basin / Melamchi River
(Location: IWMI HQ Call no: IWMI Record No: H044828)
The Melamchi Water Supply Project (MWSP) is designed to minimize the shortage of drinking water in the Kathmandu valley. Although the project was supposed to be completed by 2008, due to various problems, it is still diffi cult to forecast the exact date of completion. This paper quantifi es the downstream effects of diverting water from the Melamchi (Stage-I),Yangri (Stage-II) and Larke (Stage-III) rivers under current as well as future climate scenarios. The Soil Water Assessment Tool (SWAT) was used in the analysis. Result shows that in the Stage-I water transfer plan, average infl ow reduction in the immediate downstream sub-basin in the dry and wet seasons are 36% and 7% respectively, where as in Stage-II the infl ow reductions are 38% for the dry season and 8% for the wet season. In Stage-III, infl ow reductions are 38% in the dry season and 7% in the wet season. The impact of the water transfer schemes on various changes in water management within the Melamchi River irrigation command area was also tested. BUDGET (soil, water and salt balance) model was used to quantify crop water requirement of Melamchi River command area when the irrigated area is increased and the cropping pattern is changed. Simulation results of crop water requirement in intensive water use conditions show that present Melamchi River command area can be increased by 2.2 times under current climate projection, whereas the area can be increased 1.4 times in 2030s and by 2.0 times in 2050s.
3 Lacombe, Guillaume; Smakhtin, Vladimir; Hoanh, Chu Thai. 2013. Wetting tendency in the Central Mekong Basin consistent with climate change-induced atmospheric disturbances already observed in East Asia. Theoretical and Applied Climatology, 111(1-2):251-263. [doi: https://doi.org/10.1007/s00704-012-0654-6]
River basins ; Climate change ; Global warming ; Rainfall patterns ; Rainfed farming ; Dry season ; Wet season ; Crop production / Southeast Asia / Mekong River Basin
(Location: IWMI HQ Call no: e-copy only Record No: H044857)
(0.44 MB)
Regional and local trends in rainfall intensity, frequency, seasonality, and extremes were analyzed in the central Mekong Basin in continental Southeast Asia over the period 1953–2004 using the modified Mann–Kendall test, accounting for long-term persistence and the regional average of the Kendall’s statistic. Regionally significant and insignificant wetting tendencies of the dry and wet seasons, respectively, were found to be consistent with rainfall alterations in the neighboring southeastern part of China and attributed by previous studies to the weakening of the East Asia Summer and Winter Monsoons. These observations suggest the existence of causal links between global warming and rainfall changes observed in continental Southeast Asia. Although these changes most likely did not alter agricultural production, they confirm the need to account for climate change impacts when assessing water resources availability in this region under rapid economic development.
4 World Bank. 2010. The Zambezi River Basin: a multi-sector investment opportunities analysis. Vol. 2 - Basin development scenarios. Washington, DC, USA: World Bank. 86p.
River basin development ; Investment ; Population ; Reservoirs ; Models ; Economic analysis ; Water power ; Energy generation ; Water supply ; Irrigation programs ; Irrigation development ; Irrigation sites ; Climate change ; Precipitation ; Flooding ; Sensitivity analysis ; Crops ; Wet season ; Dry season ; Flow discharge / Africa / Zambezi River Basin
(Location: IWMI HQ Call no: e-copy only Record No: H044944)
http://www-wds.worldbank.org/external/default/WDSContentServer/WDSP/IB/2010/12/14/000333038_20101214043612/Rendered/PDF/584040V20WP0Wh1evelopment0Scenarios.pdf?
https://vlibrary.iwmi.org/pdf/H044944.pdf
https://vlibrary.iwmi.org/pdf/H044944.pdf
(7.71 MB) (7.7MB)
The Zambezi River Basin (ZRB) is one of the most diverse and valuable natural resources in Africa. Its waters are critical to sustainable economic growth and poverty reduction in the region. In addition to meeting the basic needs of some 30 million people and sustaining a rich and diverse natural environment, the river plays a central role in the economies of the eight riparian countries—Angola, Botswana, Malawi, Mozambique, Namibia, Tanzania, Zambia, and Zimbabwe. It provides important environmental goods and services to the region and is essential to regional food security and hydropower production. Because the Zambezi River Basin is characterized by extreme climatic variability, the River and its tributaries are subject to a cycle of floods and droughts that have devastating effects on the people and economies of the region, especially the poorest members of the population.
5 Mekong River Commission Secretariat. 1994. Irrigation rehabilitation study in Cambodia: inventory and analyses of existing systems. Vol. 1 - Main report. Bangkok, Thailand: Sir William Halcrow and Partners. 19p. + appendixes.
Irrigation systems ; Rehabilitation ; Irrigated sites ; Irrigated farming ; Water resources ; Water availability ; Soils ; Rice ; Agricultural production ; Cropping systems ; Cropping patterns ; Reservoir, ; Canals ; Catchment areas ; Runoff ; Assessment ; Land suitability ; Land use ; Dry season ; Wet season ; Development projects ; Soils ; Organizations ; Economic aspects / Cambodia
(Location: IWMI HQ Call no: e-copy only Record No: H045738)
(2.72 MB)
6 Tuong, T. P.; Humphreys, E.; Khan, Z. H.; Nelson, A.; Mondal, M.; Buisson, Marie-Charlotte; George, P. 2014. Messages from the Ganges Basin development challenge: unlocking the production potential of the polders of the coastal zone of Bangladesh through water management investment and reform. Colombo, Sri Lanka: CGIAR Challenge Program on Water and Food (CPWF). 32p.
Water management ; Water resources ; Water governance ; Coastal area ; River basin development ; Investment ; Cropping systems ; Drainage ; Climate change ; Dry season ; Wet season ; Aquaculture ; Agriculture ; Reclaimed land / Bangladesh
(Location: IWMI HQ Call no: e-copy only Record No: H046498)
http://r4d.dfid.gov.uk/pdf/outputs/WaterfoodCP/CPWF-Ganges-basin-messages-final.pdf
https://vlibrary.iwmi.org/pdf/H046498.pdf
https://vlibrary.iwmi.org/pdf/H046498.pdf
(1.16 MB)
7 Haile, Alemseged Tamiru; Yan, F.; Habib, E. 2015. Accuracy of the CMORPH satellite-rainfall product over Lake Tana Basin in eastern Africa. Atmospheric Research, 163:177-187. [doi: https://doi.org/10.1016/j.atmosres.2014.11.011]
Rain ; Satellites ; River basins ; Lakes ; Remote sensing ; Spatial distribution ; Wet season ; Dry season / Eastern Africa / Lake Tana Basin
(Location: IWMI HQ Call no: e-copy only Record No: H046880)
In this study, we assessed the accuracy of rainfall occurrence, amount and distribution over the Lake Tana basin in Ethiopia, Eastern Africa, as represented in the NOAA satellite-based Climate Prediction Center Morphing technique (CMORPH) rainfall product. This analysis is carried out at high spatial and temporal resolutions (8 × 8 km2 and daily) using observations from rain gauges as a reference for the period covering January 2003 to December 2006. Graphical comparisons and several statistical metrics such as bias, correlation coefficient, and standard deviation of rainfall differences are used to perform the evaluation analysis. Spatial maps of these statistical metrics were developed to assess the spatial dependency in the CMORPH accuracy. The bias is decomposed into different components, hit, missed, and false, in order to gain additional insight into the possible sources of systematic deviations in CMORPH. Overall, CMORPH was able to capture the seasonal and spatial patterns of rainfall over the basin, but with varying degrees of accuracy that depend on topography, latitude and lake-versus-land conditions within the basin. The results show that CMORPH captured rain occurrence relatively well in both wet and dry seasons over the southern part of the basin but it significantly overestimated those over the lake and its southern shore. The bias of CMORPH in the study area is characterized by seasonal and spatial variations (-25 to 30% in wet season and -40 to 60% in dry season). False as well as missed rains contribute significantly to the total rainfall amounts over the basin. Significant levels of the differences are observed at the daily resolution of CMORPH. The relation between CMORPH and gauge rainfall amounts is stronger (correlationmostly N0.4) in thewet season than in the dry (mostly b0.4).
8 Rink, Paul; Manthrithilake, Herath. 2015. The potential benefits of rainwater harvesting for households in the Jaffna peninsula [Abstract only] In Sri Lankan Association for Fisheries and Aquatic Resources (SLAFAR). Proceedings of the Twenty-first Scientific Sessions of the Sri Lanka Association for Fisheries and Aquatic Resources, Colombo, Sri Lanka, 22 May 2015. Abstracts of Papers. Colombo, Sri Lanka: Sri Lankan Association for Fisheries and Aquatic Resources (SLAFAR). pp.48.
Rain ; Water harvesting ; Drinking water ; Domestic water ; Households ; Calculators ; Dry season ; Wet season ; Groundwater ; Cost benefit analysis / Sri Lanka / Jaffna
(Location: IWMI HQ Call no: e-copy only Record No: H047081)
(0.07 MB)
Recent development activities in the Jaffna Peninsula are threatening the viability of the region's natural groundwater supply. Rainwater Harvesting (RWH) represents one important approach to remedying this situation. By accumulating freshwater during Jaffna's wet season, household RWH systems can supply drinking and cooking water for use during the water-limited dry season. Additionally, a RWH calculator created by the International Water Management Institute (IWMI) can be used to customize a RWH system for each family given particular household parameters such as rooftop size and daily extraction rate. When paired with cost estimates for tank construction, a RWH installation cost-benefit analysis can be determined for either a specific household or for a collection of households within the Jaffna region.
9 Sander, B. O.; Wassmann, R.; Siopongco, J. D. L. C. 2015. Mitigating greenhouse gas emissions from rice production through water-saving techniques: potential, adoption and empirical evidence. In Hoanh, Chu Thai; Johnston, Robyn; Smakhtin, Vladimir. Climate change and agricultural water management in developing countries. Wallingford, UK: CABI. pp.193-207. (CABI Climate Change Series 8)
Greenhouse gases ; Methane emission ; Nitrous oxide ; Crop production ; Flood irrigation ; Rice ; Water conservation ; Water management ; Farmers ; Wet season ; Dry season
(Location: IWMI HQ Call no: IWMI Record No: H047379)
(599 KB)
10 Johnston, Robyn; Try, T.; de Silva, Sanjiv. 2013. Agricultural water management planning in Cambodia. Colombo, Sri Lanka: International Water Management institute (IWMI) 12p. (IWMI-ACIAR Investing in Water Management to Improve Productivity of Rice-based Farming Systems in Cambodia Project. Issue Brief 1)
Agriculture ; Water management ; Economic development ; Supplemental irrigation ; Dry season ; Wet season ; Food security ; Rice ; Poverty ; Farmers ; Investment planning ; Pumping / Cambodia
(Location: IWMI HQ Call no: e-copy only Record No: H047419)
(3.23 MB)
11 de Silva, Sanjiv; Johnston, Robyn; Try, T. 2013. Rice and fish: impacts of intensification of rice cultivation. Colombo, Sri Lanka: International Water Management institute (IWMI). 8p. (IWMI-ACIAR Investing in Water Management to Improve Productivity of Rice-based Farming Systems in Cambodia Project. Issue Brief 4)
Crop production ; Rice ; Cultivation ; Aquaculture ; Fisheries ; Intensification ; Pesticides ; Farmers ; Wet season ; Reservoir operation / Cambodia
(Location: IWMI HQ Call no: e-copy only Record No: H047422)
(980 KB)
12 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.
13 Assefa, S.; Biazin, B.; Muluneh, A.; Yimer, F.; Haileslassie, Amare. 2016. Rainwater harvesting for supplemental irrigation of onions in the southern dry lands of Ethiopia. Agricultural Water Management, 178:325-334. [doi: https://doi.org/10.1016/j.agwat.2016.10.012]
Rainwater ; Water harvesting ; Irrigation systems ; Supplemental irrigation ; Vegetables ; Onions ; Arid zones ; Dry season ; Wet season ; Dry spells ; Water productivity ; Water supply ; Water requirements ; Irrigation water ; Soil properties ; Runoff ; Planting ; Rainfed farming / Africa South of Sahara / Ethiopia / Halaba District
(Location: IWMI HQ Call no: e-copy only Record No: H047784)
14 Schafer, M. P.; Dietrich, O.; Mbilinyi, B. 2016. Streamflow and lake water level changes and their attributed causes in eastern and southern Africa: state of the art review. International Journal of Water Resources Development, 32(6):853-880. [doi: https://doi.org/10.1080/07900627.2015.1091289]
Water resources ; Water levels ; Water use ; Stream flow ; Lakes ; Dams ; Flooding ; Land use ; Land cover change ; Climate change ; Rain ; Catchment areas ; Drainage ; River basins ; Dry season ; Wet season ; Agriculture ; Hydrology ; Case studies ; Literature reviews / Eastern Africa / Southern Africa
(Location: IWMI HQ Call no: e-copy only Record No: H047797)
(3.62 MB)
The objective of this review is to evaluate recent quantitative changes in streamflow and lake water levels in drainage basins of Eastern and Southern Africa. Findings indicate that the majority of analyzed case studies report decreasing streamflow or lake water levels between 1970 and 2010. The causes of change are chiefly anthropogenic, namely water withdrawal, land use and land cover change, and dams, and only to a lesser degree climate-related. However, there are distinct regional and temporal differences regarding reported changes and causes, e.g. land use and land cover change being mainly attributed to Eastern Africa, and dams to Southern Africa.
15 Rasanen, T. A.; Someth, P.; Lauri, H.; Koponen, J.; Sarkkula, J.; Kummu, M. 2017. Observed river discharge changes due to hydropower operations in the Upper Mekong Basin. Journal of Hydrology, 545:28-41. [doi: https://doi.org/10.1016/j.jhydrol.2016.12.023]
Water power ; International waters ; Rivers ; Downstream ; Flow discharge ; Development projects ; Hydrological factors ; Models ; Water levels ; Dams ; Reservoirs ; Dry season ; Wet season / Thailand / Cambodia / Upper Mekong Basin / Chiang Saen / Nakhon Phanom / Kratie
(Location: IWMI HQ Call no: e-copy only Record No: H048004)
(1.55 MB)
The Upper Mekong Basin is undergoing extensive hydropower development and its largest dams have recently become operational. Hydropower is built to improve the regional energy supply, but at the same time, it has considerable transboundary impacts on downstream discharge regime and further on aquatic ecosystems, riparian livelihoods and food security. Despite the transboundary significance of the impacts, there is no public information on the hydropower operations or on the already observed downstream discharge impacts since the completion of the largest dams. Therefore, in this study we assess the discharge changes using observed river discharge data and a distributed hydrological model over the period of 1960–2014. Our findings indicate that the hydropower operations have considerably modified the river discharges since 2011 and the largest changes were observed in 2014. According to observed and simulated discharges, the most notable changes occurred in northern Thailand (Chiang Saen) in March-May 2014 when the discharge increased by 121–187% and in July-August 2014 when the discharge decreased by 32–46% compared to average discharges. The respective changes in Cambodia (Kratie) were 41–74% increase in March-May 2014 and 0–6% decrease in July-August 2014 discharges. The earlier model-based predictions of the discharge changes are well in line with the observed changes, although observed changes are partly larger. The discharge impacts are expected to vary from year to year depending on hydropower operations. Altogether, the results highlight the need for strong transboundary cooperation for managing the downstream impacts.
16 Lacombe, Guillaume; Polthanee, A.; Trebuil, G. 2017. Long-term change in rainfall distribution in northeast Thailand: will cropping systems be able to adapt? Cahiers Agricultures, 26(2):1-10. [doi: https://doi.org/10.1051/cagri/2017006]
Cropping systems ; Farming systems ; Climate change adaptation ; Monsoon climate ; Rainfall patterns ; Dry season ; Wet season ; Meteorological stations ; Farmers / Thailand
(Location: IWMI HQ Call no: e-copy only Record No: H048065)
http://www.cahiersagricultures.fr/articles/cagri/pdf/2017/02/cagri160180.pdf
https://vlibrary.iwmi.org/pdf/H048065.pdf
https://vlibrary.iwmi.org/pdf/H048065.pdf
(1.81 MB)
Climate vagaries and the lack of irrigation, frequently combined with coarse-textured sandy and unevenly distributed saline soils, explain low crop yields and the endemic relative poverty of the rural population in Northeast Thailand (NET). Local and regional trends in agriculturally-relevant rainfall variables were investigated using the Mann-Kendall test, modified to account for serial correlation, and applied to 17 stations across NET, and the regional average Kendall's statistic. Limited changes in rainfall frequency, intensity and seasonality are observed at individual stations over the study period (1953–2004). But we found a significant regional trend toward a wetter dry season. Based on an intimate knowledge of the local farming systems, we discuss the cropping systems adaptation to these rainfall changes. If the wetting of the dry season extends in the future, as expected according to most climate projections, households would not find it difficult to adapt, except for the problems caused by temperature rise, mainly due to their renowned adaptive capacity and high mobility that historically produced diverse and resilient rural livelihood systems.
17 Amoah, Philip; Adamtey, N.; Cofie, Olufunke. 2017. Effect of urine, poultry manure, and dewatered faecal sludge on agronomic characteristics of cabbage in Accra, Ghana. Resources, 6(2):1-14. [doi: https://doi.org/10.3390/resources6020019]
Soil chemicophysical properties ; Soil analysis ; Chemical analysis ; Fertilizer application ; pH ; Urine ; Poultry droppings ; Organic fertilizers ; Faecal sludge ; Agronomic characters ; Nutrient uptake ; Urban agriculture ; Cabbages ; Nitrogen fertilizers ; Wet season ; Farmers ; Environmental pollution ; Water pollution / Ghana / Accra
(Location: IWMI HQ Call no: e-copy only Record No: H048132)
(1.39 MB)
The study was to assess the: (i) effect of human urine and other organic inputs on cabbage growth, yield, nutrient uptake, N-use efficiency, and soil chemical characteristics; (ii) economic returns of the use of urine and/or other organic inputs as a source of fertiliser for cabbage production. To meet these objectives, participatory field trials were conducted at Dzorwulu, Accra. Four different treatments (Urine alone, Urine + dewatered faecal sludge (DFS), Urine + poultry droppings (PD), NPK (15-15-15) + PD) were applied in a Randomised Complete Block Design (RCBD) with soil alone as control. Each treatment was applied at a rate of 121 kg·N·ha-1 corresponding to the Nitrogen requirement of cabbage in Ghana. Growth and yield parameters, plant nutrient uptake, and soil chemical characteristics were determined using standard protocols. There were no significant differences between treatments for cabbage head weight, or total and marketable yields. However, unmarketable yield from NPK + PD was 1 to 2 times higher (p < 0.05) than those from Urine + PD, Urine + DFS, and Urine alone. Seasonal effect on yields was also pronounced with higher (p < 0.001) cabbage head weight (0.95 kg) and marketable yields (12.7 kg·ha-1) in the dry season than the rainy season (0.42 kg and 6.27 kg·ha-1). There was higher (p < 0.005) phosphorous uptake in cabbage from Urine + PD treated soil than those from other treatments. Nitrogen (N), phosphorous (P), and potassium (K) uptake in the dry season was significantly higher than the rainy season. Soils treated with Urine + DFS and Urine + PD were high in total N content. Urine + PD and Urine + DFS treated soils gave fairly high yield than PD + NPK with a net gain of US$1452.0 and US$1663.5, respectively. The application of urine in combination with poultry droppings has the potential to improve cabbage yields, nutrient uptake, and soil nitrogen and phosphorous content.
18 Lyon, S. W.; King, K.; Polpanich, O.; Lacombe, Guillaume. 2017. Assessing hydrologic changes across the Lower Mekong Basin. Journal of Hydrology: Regional Studies, 12:303-314. [doi: https://doi.org/10.1016/j.ejrh.2017.06.007]
Hydrological factors ; Catchment areas ; River basins ; Models ; Natural resources ; Forest cover ; Deforestation ; Rainfall-runoff relationships ; Wet season ; Dry season ; Evapotranspiration ; Rice ; Land cover ; Stream flow ; Precipitation / Southeast Asia / Lao People's Democratic Republic / Thailand / Cambodia / Vietnam / Lower Mekong Basin
(Location: IWMI HQ Call no: e-copy only Record No: H048179)
http://ac.els-cdn.com/S2214581816302348/1-s2.0-S2214581816302348-main.pdf?_tid=fbab4f94-9de3-11e7-b294-00000aacb362&acdnat=1505898996_0cb0f1fe6d4c4991593d85d0efcf7e92
https://vlibrary.iwmi.org/pdf/H048179.pdf
https://vlibrary.iwmi.org/pdf/H048179.pdf
(906 KB)
Study region : In this study, 33 catchments across the Lower Mekong Basin in Southeast Asia are examined to detect historical changes in their hydrological response via a model-based methodology.
Study focus : Intensive development over the past half century across Southeast Asia’s Lower Mekong Basin has inevitably affected natural resources. Large areas have been converted from forests for subsistence and commercial agriculture, and urban development. We implement an innovative approach to screen hydrologic data for detecting impacts of such large-scale changes on hydrological response. In a first step, temporal changes in the rainfall-runoff relationship were assessed using the parsimonious, two-parameter GR2M hydrological model. In a second step, a distribution-free statistical test was applied to detect whether significant changes have occurred in the wet season (high flow) and dry season (low flow) conditions.
New hydrological insights for the region : Our results indicate that the majority of catchments (64% of those considered) with sufficiently long data records exhibited no discernable trends in hydrological response. Those catchments that did exhibit significant trends in hydrological response were fairly evenly split between increasing trends (between 21% and 24%) and decreasing trends (between 15% and 12%) with time. There was a lack of evidence that these changes where brought about by shifts in precipitation or potential evapotranspiration; however, catchments exhibiting significant increasing trends in hydrological behavior were found to have different land cover compositions (lower percentage of forest coverage and subsequently higher paddy rice coverage) than those exhibiting significant decreasing trends. The approach presented here provides a potentially valuable screening method to highlight regions for further investigation of improved mechanistic understanding. Without this connection, we might be blind to future hydrological shifts that can have significant impact on development.
Study focus : Intensive development over the past half century across Southeast Asia’s Lower Mekong Basin has inevitably affected natural resources. Large areas have been converted from forests for subsistence and commercial agriculture, and urban development. We implement an innovative approach to screen hydrologic data for detecting impacts of such large-scale changes on hydrological response. In a first step, temporal changes in the rainfall-runoff relationship were assessed using the parsimonious, two-parameter GR2M hydrological model. In a second step, a distribution-free statistical test was applied to detect whether significant changes have occurred in the wet season (high flow) and dry season (low flow) conditions.
New hydrological insights for the region : Our results indicate that the majority of catchments (64% of those considered) with sufficiently long data records exhibited no discernable trends in hydrological response. Those catchments that did exhibit significant trends in hydrological response were fairly evenly split between increasing trends (between 21% and 24%) and decreasing trends (between 15% and 12%) with time. There was a lack of evidence that these changes where brought about by shifts in precipitation or potential evapotranspiration; however, catchments exhibiting significant increasing trends in hydrological behavior were found to have different land cover compositions (lower percentage of forest coverage and subsequently higher paddy rice coverage) than those exhibiting significant decreasing trends. The approach presented here provides a potentially valuable screening method to highlight regions for further investigation of improved mechanistic understanding. Without this connection, we might be blind to future hydrological shifts that can have significant impact on development.
19 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.
20 Kadyampakeni, Davie M.; Mul, Marloes L.; Obuobie, E.; Appoh, Richard; Owusu, Afua; Ghansah, Benjamin; Boakye-Acheampong, Enoch; Barron, Jennie. 2017. Agro-climatic and hydrological characterization of selected watersheds in northern Ghana. Colombo, Sri Lanka: International Water Management Institute (IWMI). 40p. (IWMI Working Paper 173) [doi: https://doi.org/10.5337/2017.209]
Watersheds ; Agricultural production ; Intensification ; Agroclimatology ; Hydrology ; Analytical method ; Agronomic practices ; Water balance ; Water quality ; Water management ; Water deficit ; Climatic factors ; pH ; Electrical conductivity ; Soil texture ; Soil quality ; Soil sampling ; Soil fertility ; Land cover mapping ; Land use ; Rain ; Temperature ; Evapotranspiration ; Farmers ; Wet season ; Dry season ; Reservoir storage ; Wells ; Rivers ; Irrigation schemes ; Catchment areas ; Cropping systems ; Crop production ; Meteorological stations ; Cation exchange capacity / Ghana
(Location: IWMI HQ Call no: IWMI Record No: H048209)
(1 MB)
This paper provides the climatic and biophysical context of three watersheds in northern Ghana. The objective of the study is to describe the agro-climatic and hydrological features of the watersheds from a landscape perspective. The analyses show that water surplus occurs about 3 months in a year, with only one month providing a significant surplus. Small-scale irrigation is, therefore, carried out in the dry months between November and June. The quality of water used for irrigation from wells, reservoirs and rivers is good for irrigation and domestic purposes. The soil chemical parameters across the study sites show that the soils are suitable for irrigation and crop system intensification, although it requires substantial fertilizer inputs. The paper concludes that there are opportunities from both a soil quality and water availability perspective to enhance sustainable intensification through small- and medium-scale irrigation in the selected watersheds.
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