Your search found 4 records
1 Nagabhatla, N.; Finlayson, C. M.; Senaratna Sellamuttu, Sonali. 2012. Assessment and change analyses (1987-2002) for tropical wetland ecosystem using earth observation and socioeconomic data. European Journal of Remote Sensing, 45:215-232.
Wetlands ; Ecosystems ; Coastal area ; Tropical zones ; Marshes ; Lagoons ; Rain ; Analytical methods ; Data analysis ; Land use ; Land cover ; Socioeconomic environment ; Vegetation / Sri Lanka / Muthrajawela Marsh / Negombo Lagoon
(Location: IWMI HQ Call no: e-copy only Record No: H044959)
http://server-geolab.agr.unifi.it/public/completed/2012_EuJRS_45_215_232_Nagabhatla.pdf
https://vlibrary.iwmi.org/pdf/H044959.pdf
https://vlibrary.iwmi.org/pdf/H044959.pdf
(2.74 MB) (2.80MB)
The two components of the study reflect assessment and change analysis of a tropical wetland in Sri Lanka. The first section explains spatial classification using pixel level-disaggregated image analysis and refined aggregated image analysis and comparison of information extracted by all methods to analyse a better classifier. The second section illustrates change analysis calibrating the land change modeller (LCM) [IDRISI-Andes]. Key observations: a) visual interpretation provides comprehensive blueprint of the wetlandscape compared to supervised and unsupervised classifiers b) change in landscape pattern reflect substantial transition in wetland use. Validation using field coordinates and socioeconomic data showed kappa value (%) of 87.
2 Yira, Y.; Diekkruger, B.; Steup, G.; Bossa, A. Y. 2016. Modeling land use change impacts on water resources in a tropical West African catchment (Dano, Burkina Faso). Journal of Hydrology, 537:187-199. [doi: https://doi.org/10.1016/j.jhydrol.2016.03.052]
Land use ; Land cover change ; Water resources ; Hydrology ; Models ; Water balance ; Groundwater ; Water levels ; Flow discharge ; Catchment areas ; Soil moisture ; Evapotranspiration ; Farmland ; Savannas ; Tropical zones ; Maps / West Africa / Burkina Faso / Dano
(Location: IWMI HQ Call no: e-copy only Record No: H047556)
(0.85 MB)
This study investigates the impacts of land use change on water resources in the Dano catchment, Burkina Faso, using a physically based hydrological simulation model and land use scenarios. Land use dynamic in the catchment was assessed through the analysis of four land use maps corresponding to the land use status in 1990, 2000, 2007, and 2013. A reclassification procedure levels out differences between the classification schemes of the four maps. The land use maps were used to build five land use scenarios corresponding to different levels of land use change in the catchment. Water balance was simulated by applying the Water flow and balance Simulation Model (WaSiM) using observed discharge, soil moisture, and groundwater level for model calibration and validation. Model statistical quality measures (R2 , NSE and KGE) achieved during calibration and validation ranged between 0.6 and 0.9 for total discharge, soil moisture, and groundwater level, indicating a good agreement between observed and simulated variables. After a successful multivariate validation the model was applied to the land use scenarios. The land use assessment exhibited a decrease of savannah at an annual rate of 2% since 1990. Conversely, cropland and urban areas have increased. Since urban areas occupy only 3% of the catchment it can be assumed that savannah was mainly converted to cropland. The conversion rate of savannah was lower than the annual population growth of 3%. A clear increase in total discharge (+17%) and decrease in evapotranspiration ( 5%) was observed following land use change in the catchment. A strong relationship was established between savannah degradation, cropland expansion, discharge increase and reduction of evapotranspiration. The increase in total discharge is related to high peak flow, suggesting (i) an increase in water resources that are not available for plant growth and human consumption and (ii) an alteration of flood risk for both the population within and downstream of the catchment.
3 Hasan, E.; Tarhule, A.; Kirstetter, P.-E.; Clark, R. III; Hong, Y. 2018. Runoff sensitivity to climate change in the Nile River Basin. Journal of Hydrology, 561:312-321. [doi: https://doi.org/10.1016/j.jhydrol.2018.04.004]
Surface runoff ; Climate change ; Water resources ; River basins ; Temperature ; Precipitation ; Evapotranspiration ; Elasticity ; Models ; Arid zones ; Tropical zones ; Sensitivity analysis / Africa / Nile River Basin
(Location: IWMI HQ Call no: e-copy only Record No: H048792)
(3.60 MB)
In data scarce basins, such as the Nile River Basin (NRB) in Africa, constraints related to data availability, quality, and access often complicate attempts to estimate runoff sensitivity using conventional methods. In this paper, we show that by integrating the concept of the aridity index (AI) (derived from the Budyko curve) and climate elasticity, we can obtain the first order response of the runoff sensitivity using minimal data input and modeling expertise or experience. The concept of runoff elasticity relies on the fact that the energy available for evapotranspiration plays a major role in determining whether the precipitation received within a drainage basin generates runoff. The approach does not account for human impacts on runoff modification and or diversions. By making use of freely available gauge-corrected satellite data for precipitation, temperature, runoff, and potential evapotranspiration, we derived the sensitivity indicator ( ) ß to determine the runoff response to changes in precipitation and temperature for four climatic zones in the NRB, namely, tropical, subtropical, semiarid and arid zones. The proposed sensitivity indicator can be partitioned into different elasticity components i.e: precipitation (ep), potential evapotranspiration (eETp), temperature (eT ) and the total elasticity ( ) etot . These elasticities allow robust quantification of the runoff response to the potential changes in precipitation and temperature with a high degree of accuracy. Results indicate that the tropical zone is energy-constrained with low sensitivity, ( 1.0) ß < , implying that input precipitation exceeds the amounts that can be evaporated given the available energy. The subtropical zone is subdivided into two distinct regions, the lowland (Machar and Sudd marshes), and the highland area (Blue Nile Basin), where each area has a unique sensitivity. The lowland area has high sensitivity, ( 1.0) ß > . The subtropical-highland zone moves between energy-limited to water-limited conditions during periods of wet and dry spells with varying sensitivity. The semiarid and arid zones are water limited, with high sensitivity, ( 1.0) ß > . The calculated runoff elasticities show that a 10% decrease in precipitation leads to a decrease in runoff of between 19% in the tropical zone and 30% in the arid zones. On the other hand, a 10% precipitation increase leads to a runoff increase of 14% in the tropical zone and 22% in the arid zone. The estimated runoff changes are consistent with the result obtained using other methods. Thus, the elasticity approach combines data parsimony and analytical simplicity to produce results that are practically useful for most purposes while facilitating communication with stakeholders with different levels of scientific knowledge. More research is needed to extend the application of the method to incorporate the effects of human activities, and land use change.
4 Foster, S.; Bousquet, A.; Furey, S. 2018. Urban groundwater use in tropical Africa - a key factor in enhancing water security? Water Policy, 20(5):982-994. [doi: https://doi.org/10.2166/wp.2018.056]
Groundwater ; Water use ; Water security ; Urban areas ; Water resources ; Water availability ; Water supply ; Boreholes ; Tropical zones ; Urbanization ; Water policy ; Databases ; Evaluation / Africa
(Location: IWMI HQ Call no: e-copy only Record No: H048953)
(0.23 MB)
A regional scoping study has reviewed the limited data on groundwater use for 10 cities in Tropical Africa. In those cities where the water utility has been able to develop groundwater rationally, the public water-supply usually offers a better service at lower cost by enabling phased investment and avoiding advanced treatment, and offers greater water-source security in drought and from pollution. Urban dwellers obtain water from multiple sources, according to availability and affordability. Among the more affluent, private water-supply boreholes are increasingly used to improve security and reduce cost but in the absence of international charity finance groundwater access is beyond the financial reach of the urban poor, except where the water table is shallow allowing the use of low-cost dugwells. The way forward must be to integrate more effectively utility and private investments, and piped and non-piped solutions, for urban water-supply provision, and for water utilities to establish low-income (‘pro-poor’) policy and technical units to pursue ways of supporting alternative water-supply provision, including advisory services and regulatory functions (where appropriate) for private borehole and dugwell use. To facilitate this, water utilities will need to partner with resource regulators and knowledge centres, which may require modifications to their mandate.
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