Your search found 8 records
1 Karimi, P.; Bastiaanssen, Wim G. M.; Sood, Aditya; Hoogeveen, J.; Peiser, L.; Bastidas-Obando, E.; Dost, R. J. 2015. Spatial evapotranspiration, rainfall and land use data in water accounting - Part 2: reliability of water acounting results for policy decisions in the Awash Basin. Hydrology and Earth System Sciences, 19:533-550. [doi: https://doi.org/10.5194/hess-19-533-2015]
Water accounting ; Land use ; Rain ; Evapotranspiration ; Policy making ; Decision making ; River basins ; Remote sensing ; Satellite surveys ; Indicators ; Hydrology ; Case studies / Ethiopia / Awash Basin
(Location: IWMI HQ Call no: e-copy only Record No: H046821)
http://www.hydrol-earth-syst-sci.net/19/533/2015/hess-19-533-2015.pdf
https://vlibrary.iwmi.org/pdf/H046821.pdf
https://vlibrary.iwmi.org/pdf/H046821.pdf
(6.95 MB) (6.95 MB)
Water Accounting Plus (WA+) is a framework that summarizes complex hydrological processes and water management issues in river basins. The framework is designed to use satellite-based measurements of land and water variables and processes as input data. A general concern associated with the use of satellite measurements is their accuracy. This study focuses on the impact of the error in remote sensing measurements on water accounting and information provided to policy makers. The Awash Basin in the central Rift Valley in Ethiopia is used as a case study to explore the reliability of WA+ outputs, in the light of input data errors. The Monte Carlo technique was used for stochastic simulation of WA+ outputs over a period of 3 yr. The results show that the stochastic mean of the majority of WA+ parameters and performance indicators are within 5 % deviation from the original WA+ values based on one single calculation. Stochastic computation is proposed as a standard procedure for WA+ water accounting because it provides the uncertainty bandwidth for every WA+ output, which is essential information for sound decision-making processes. The majority of WA+ parameters and performance indicators have a coefficient of variation (CV) of less than 20 %, which implies that they are reliable and provide consistent information on the functioning of the basin. The results of the Awash Basin also indicate that the utilized flow and basin closure fraction (the degree to which available water in a basin is utilized) have a high margin of error and thus a low reliability. As such, the usefulness of them in formulating important policy decisions for the Awash Basin is limited. Other river basins will usually have a more accurate assessment of the discharge in the river mouth.
2 Karimi, P.; Bastiaanssen, Wim G. M. 2015. Spatial evapotranspiration, rainfall and land use data in water accounting - Part 1: review of the accuracy of the remote sensing data. Hydrology and Earth System Sciences, 19:507-532. [doi: https://doi.org/10.5194/hess-19-507-2015]
Water accounting ; Water balance ; Land use ; Rain ; Evapotranspiration ; Remote sensing ; Satellite surveys ; River basins ; Hydrology ; Models
(Location: IWMI HQ Call no: e-copy only Record No: H046824)
http://www.hydrol-earth-syst-sci.net/19/507/2015/hess-19-507-2015.pdf
https://vlibrary.iwmi.org/pdf/H046824.pdf
https://vlibrary.iwmi.org/pdf/H046824.pdf
(0.50 MB) (515 KB)
The scarcity of water encourages scientists to develop new analytical tools to enhance water resource management. Water accounting and distributed hydrological models are examples of such tools. Water accounting needs accurate input data for adequate descriptions of water distribution and water depletion in river basins. Ground-based observatories are decreasing, and not generally accessible. Remote sensing data is a suitable alternative to measure the required input variables. This paper reviews the reliability of remote sensing algorithms to accurately determine the spatial distribution of actual evapotranspiration, rainfall and land use. For our validation we used only those papers that covered study periods of seasonal to annual cycles because the accumulated water balance is the primary concern. Review papers covering shorter periods only (days, weeks) were not included in our review. Our review shows that by using remote sensing, the absolute values of evapotranspiration can be estimated with an overall accuracy of 95 % (SD 5 %) and rainfall with an overall absolute accuracy of 82 % (SD 15 %). Land use can be identified with an overall accuracy of 85 % (SD 7 %). Hence, more scientific work is needed to improve the spatial mapping of rainfall and land use using multiple space-borne sensors. While not always perfect at all spatial and temporal scales, seasonally accumulated actual evapotranspiration maps can be used with confidence in water accounting and hydrological modeling.
3 Delavar, M.; Morid, S.; Morid, R.; Farokhnia, A.; Babaeian, F.; Srinivasan, R.; Karimi, P.. 2020. Basin-wide water accounting based on modified SWAT model and WA+ framework for better policy making. Journal of Hydrology, 585:124762. (Online first) [doi: https://doi.org/10.1016/j.jhydrol.2020.124762]
Water accounting ; Soil water ; Models ; Policy making ; Evapotranspiration ; Water resources ; Water conservation ; Groundwater table ; Aquifers ; Water extraction ; Irrigation management ; Remote sensing ; Land use ; Indicators / Iran Islamic Republic / Tashk-Bakhtegan Basin
(Location: IWMI HQ Call no: e-copy only Record No: H049675)
(8.75 MB)
Evaluation of water resources systems and implementation of appropriate management strategies requires accurate and well classified information describing supply, demand, and consumption. The WA+ water accounting framework is a relevant tool in this regard. Earlier applications of the WA+ framework draw heavily from remote sensing (RS) data; however, applying RS data limits the application of the framework to past and current situations. Such analyses are needed for future assessments due to new management and climate scenarios. Therefore, the objective of this research is to link WA+ with the Soil Water Assessment Tool (SWAT) model to enhance it and to evaluate water management strategies through an integrated framework. The resulting system, SWAT-FARS (customized version of SWAT model for Fars region) is capable of supporting macro and micro water planning through a systematic presentation of the past trends, current and future status in water supply and demand. To explore this methodology, the system was applied to the Tashk-Bakhtegan basin (Iran). The trends in supply and consumption within the basin and some of the water saving policies that are mandated by the country’s 6th development plan were evaluated. Application of SWAT-FARS to the Task-Bakhtegan basin showed decrease in “Manageable water” of about 23% and a simultaneous increase of “Incremental irrigation” of about 53%; this lack of accessible water and imbalance of manageable water and water usage has almost omitted the basin’s “Outflows”. To alleviate pressures on the basin’s water resources, a suggested elimination of rice cultivation and improving pressurized irrigation showed the first policy could reduce water consumption by 0.08 BCM/yr and the second one can even increase water consumption by 0.25 BCM/yr over current conditions. The methodology used to develop SWAT-FARS is strongly recommended for other regions suffering water scarcity.
4 Blatchford, M. L.; Mannaerts, C. M.; Njuki, S. M.; Nouri, H.; Zeng, Y.; Pelgrum, H.; Wonink, S.; Karimi, P.. 2020. Evaluation of WaPOR V2 evapotranspiration products across Africa. Hydrological Processes, 34(15):3200-3221. [doi: https://doi.org/10.1002/hyp.13791]
Evapotranspiration ; Water productivity ; Remote sensing ; Evaluation ; Water resources ; Water management ; Water balance ; Water availability ; Vegetation ; Uncertainty ; Precipitation ; Energy balance ; Models ; FAO / Africa / Middle East
(Location: IWMI HQ Call no: e-copy only Record No: H049920)
https://onlinelibrary.wiley.com/doi/epdf/10.1002/hyp.13791
https://vlibrary.iwmi.org/pdf/H049920.pdf
https://vlibrary.iwmi.org/pdf/H049920.pdf
(5.66 MB) (5.66 MB)
The Food and Agricultural Organization of the United Nations (FAO) portal to monitor water productivity through open-access of remotely sensed derived data (WaPOR) offers continuous actual evapotranspiration and interception (ETIa-WPR) data at a 10-day basis across Africa and the Middle East from 2009 onwards at three spatial resolutions. The continental level (250 m) covers Africa and the Middle East (L1). The national level (100 m) covers 21 countries and 4 river basins (L2). The third level (30 m) covers eight irrigation areas (L3). To quantify the uncertainty of WaPOR version 2 (V2.0) ETIa-WPR in Africa, we used a number of validation methods. We checked the physical consistency against water availability and the long-term water balance and then verify the continental spatial and temporal trends for the major climates in Africa. We directly validated ETIa-WPR against in situ data of 14 eddy covariance stations (EC). Finally, we checked the level consistency between the different spatial resolutions. Our findings indicate that ETIa-WPR is performing well, but with some noticeable overestimation. The ETIa-WPR is showing expected spatial and temporal consistency with respect to climate classes. ETIa-WPR shows mixed results at point scale as compared to EC flux towers with an overall correlation of 0.71, and a root mean square error of 1.2 mm/day. The level cotency is very high between L1 and L2. However, the consistency between L1 and L3 varies significantly between irrigation areas. In rainfed areas, the ETIa-WPR is overestimating at low ETIa-WPR and underestimating when ETIa is high. In irrigated areas, ETIa-WPR values appear to be consistently overestimating ETa. The relative soil moisture content (SMC), the input of quality layers and local advection effects were some of the identified causes. The quality assessment of ETIa-WPR product is enhanced by combining multiple evaluation methods. Based on the results, the ETIa-WPR dataset is of enough quality to contribute to the understanding and monitoring of local and continental water processes and water management.
5 Ayyad, S.; Karimi, P.; Langensiepen, M.; Ribbe, L.; Rebelo, Lisa-Maria; Becker, M. 2022. Remote sensing assessment of available green water to increase crop production in seasonal floodplain wetlands of Sub-Saharan Africa. Agricultural Water Management, 269:107712. [doi: https://doi.org/10.1016/j.agwat.2022.107712]
Water availability ; Crop production ; Remote sensing ; Assessment ; Floodplains ; Wetlands ; Evapotranspiration ; Food security ; Sustainable intensification ; Diversification ; Rainfed farming ; Rice ; Soil moisture ; Dry farming ; Farmland ; Land cover ; Livelihoods ; Datasets ; Spatial distribution / Africa South of Sahara / United Republic of Tanzania / Kilombero Valley Floodplain
(Location: IWMI HQ Call no: e-copy only Record No: H051176)
https://www.sciencedirect.com/science/article/pii/S0378377422002591/pdfft?md5=96e2483fb6a89d468995a4fd01964b6b&pid=1-s2.0-S0378377422002591-main.pdf
https://vlibrary.iwmi.org/pdf/H051176.pdf
https://vlibrary.iwmi.org/pdf/H051176.pdf
(19.50 MB) (19.5 MB)
Producing more food for a growing population requires sustainable crop intensification and diversification, particularly in high-potential areas such as the seasonal floodplain wetlands of sub-Saharan Africa (SSA). With emerging water shortages and concerns for conserving these multi-functional wetlands, a further expansion of the cropland area must be avoided as it would entail increased use of blue water for irrigation and infringe on valuable protected areas. We advocate an efficient use of the prevailing green water on the existing cropland areas, where small-scale farmers grow a single crop of rainfed lowland rice during the wet season. However, soil moisture at the onset of the rains (pre-rice niche) and residual soil moisture after rice harvest (post-rice niche) may suffice to cultivate short-cycled crops. We developed a methodological approach to analyze the potential for green water cultivation in the pre- and post-rice niches in the Kilombero Valley Floodplain in Tanzania, as a representative case for seasonal floodplain wetlands in SSA. The three-step approach used open-access remote sensing datasets to: (i) extract cropland areas; (ii) analyze soil moisture conditions using evaporative stress indices to identify the pre- and post-rice niches; and (iii) quantify the green water availability in the identified niches through actual evapotranspiration (AET).
We identified distinct patterns of green water being available both before and after the rice-growing period. Based on the analyses of evaporative stress indices, the pre-rice niche tends to be longer (~70 days with average AET of 20–40 mm/10-day) but also more variable (inter-annual variability >30%) than the post-rice niche (~65 days with average AET of 10–30 mm/10-day, inter-annual variability <15%). These findings show the large potential for cultivating short-cycled crops beyond the rice-growing period, such as green manure, vegetables, maize, and forage legumes, by shifting a portion of the nonproductive AET flows (i.e., soil evaporation) to productive flows in form of crop transpiration. A cropland area of 1452 to 1637 km2 (53–60% of the total cropland area identified of 2730 km2) could be cultivated using available green water in the dry season, which shows the significance of such change for food security, livelihoods, and resilience of the agricultural community in Kilombero. A wider application of the developed approach in this study can help identifying opportunities and guiding interventions and investments towards establishing sustainable intensification and diversification practices in floodplain wetlands in SSA.
We identified distinct patterns of green water being available both before and after the rice-growing period. Based on the analyses of evaporative stress indices, the pre-rice niche tends to be longer (~70 days with average AET of 20–40 mm/10-day) but also more variable (inter-annual variability >30%) than the post-rice niche (~65 days with average AET of 10–30 mm/10-day, inter-annual variability <15%). These findings show the large potential for cultivating short-cycled crops beyond the rice-growing period, such as green manure, vegetables, maize, and forage legumes, by shifting a portion of the nonproductive AET flows (i.e., soil evaporation) to productive flows in form of crop transpiration. A cropland area of 1452 to 1637 km2 (53–60% of the total cropland area identified of 2730 km2) could be cultivated using available green water in the dry season, which shows the significance of such change for food security, livelihoods, and resilience of the agricultural community in Kilombero. A wider application of the developed approach in this study can help identifying opportunities and guiding interventions and investments towards establishing sustainable intensification and diversification practices in floodplain wetlands in SSA.
6 Ayyad, S.; Karimi, P.; Langensiepen, M.; Ribbe, L.; Rebelo, Lisa-Maria; Becker, M. 2022. Increasing cropping options in seasonal floodplain wetlands of Sub-Saharan Africa: a remote-sensing approach for assessing available green water for cultivation [Abstract only]. Paper presented at the European Geosciences Union (EGU) General Assembly 2022, Vienna, Austria and Online, 23-27 May 2022. 2p. [doi: https://doi.org/10.5194/egusphere-egu22-3982]
Crop production ; Intensification ; Rice ; Water availability ; Farmland ; Floodplains ; Wetlands ; Remote sensing / Africa South of Sahara / United Republic of Tanzania / Kilombero Floodplain
(Location: IWMI HQ Call no: e-copy only Record No: H051441)
https://meetingorganizer.copernicus.org/EGU22/EGU22-3982.html?pdf
https://vlibrary.iwmi.org/pdf/H051441.pdf
https://vlibrary.iwmi.org/pdf/H051441.pdf
(0.29 MB) (292 KB)
7 Weitkamp, T.; Veldwisch, G. J.; Karimi, P.; de Fraiture, C. 2023. Mapping irrigated agriculture in fragmented landscapes of Sub-Saharan Africa: an examination of algorithm and composite length effectiveness. International Journal of Applied Earth Observation and Geoinformation, 122:103418. [doi: https://doi.org/10.1016/j.jag.2023.103418]
Irrigated farming ; Irrigation schemes ; Landscape ; Farmland ; Neural networks ; Remote sensing ; Smallholders ; Vegetation ; Machine learning ; Dry season / Africa South of Sahara / Mozambique
(Location: IWMI HQ Call no: e-copy only Record No: H052203)
https://www.sciencedirect.com/science/article/pii/S156984322300242X/pdfft?md5=b946334370bd2d782115718f81a74172&pid=1-s2.0-S156984322300242X-main.pdf
https://vlibrary.iwmi.org/pdf/H052203.pdf
https://vlibrary.iwmi.org/pdf/H052203.pdf
(70.70 MB) (70.7 MB)
Accurately identifying irrigated areas is crucial for sustainable development, food security, and effective land and water resource management. However, incomplete or outdated national estimates of irrigated areas underestimate the extent of it, particularly among smallholders. This study aimed to address this issue by investigating the impact of different algorithms and composite lengths on predicting irrigated agriculture in four study areas in Mozambique. The study found that the choice of algorithm and composite length notably impacted the accuracy of identifying irrigation. Shorter composite lengths, such as 2-monthly or 3-monthly composites, were more effective in identifying irrigation in fragmented and dynamic landscapes, while longer composite lengths were better suited to stable classes and homogeneous landscapes. Artificial neural networks, support vector machines, and random forests were all effective algorithms for classifying irrigation. However, the study emphasised the importance of considering hotspots and agreement maps when identifying irrigation. Agreement maps combine the classification results of multiple models, providing better insights into the core areas of irrigated agriculture and allowing for a better understanding of irrigation dynamics and policy decision-making, particularly among smallholder systems. This research provides valuable insights for those working on remote sensing-based irrigation mapping and monitoring in sub-Saharan Africa, focusing on identifying smallholder irrigation with greater certainty.
8 Yalew, S. G.; van der Zaag, P.; Tran, B. N.; Michailovsky, C. I. B.; Salvadore, E.; Borgomeo, E.; Karimi, P.; Pareeth, S.; Seyoum, S. D.; Mul, M. L. 2023. Open-access remote sensing data for cooperation in transboundary water management. Water International, 21p (Online first) [doi: https://doi.org/10.1080/02508060.2023.2263226]
Remote sensing ; Transboundary waters ; Water management ; Water resources ; Cooperation ; Cooperatives ; Conflicts ; Models ; Evapotranspiration ; Precipitation ; Monitoring ; Agreements ; Water balance ; Uncertainty ; Water accounting ; Water quality ; Land cover ; Surface water ; Water levels ; Water storage ; Water reservoirs
(Location: IWMI HQ Call no: e-copy only Record No: H052284)
(1.38 MB)
Open-access remote sensing products provide data for transboundary water management. This study presents a comprehensive overview of the applications, uncertainties and implications of these remote sensing data products in the context of transboundary water management. Focusing on different stages within the transboundary cooperation continuum, we delineate the potential role and application of remote sensing data at the various stages of this cooperation. Despite the uncertainties and capacity requirements for data acquisition, processing and interpretation, we argue that remote sensing broadens opportunities to monitor, assess, forecast, track or validate compliance in transboundary basins, thereby challenging traditional notions of water data exclusivity.
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