Using Satellite Remote Sensing to Assess Evapotranspiration: Case Study of the Upper Ewaso Ng’iro North Basin, Kenya.
Actual Evapotranspiration (ETa) is one of the most useful indicators to explain whether the water is being used as “intended”. ETa variations, both in space and time and from different land use types are seen to be highly indicative for the adequacy, reliability and equity in water use; the knowledge of these terms is essential for judicious water resources management. Unfortunately, ETa estimation under actual field conditions is still a big challenge to both scientists and water managers. The complexity associated with the estimation of ETa has lead to the development of various methodological approaches for estimating it over time. During the last two to three decades, significant progress has been made to estimate actual evapotranspiration using satellite remote sensing These methods provide a powerful means to compute ETa from pixel to the entire basin scale. In this study, Surface Energy Balance Algorithm for Land (SEBAL) was used to compute a complete radiation and energy balance along with the resistances for momentum, heat and water vapour transport for each pixel and then applied to assess the ETa at the basin scale and subsequently carryout a simple water balance for the basin. This was done for the Upper Ewaso Ng’iro North River Basin, in Kenya. Landcover/landuse for 2000, 2003 and 2006 were assessed and compared with ETa for the same periods and a significant correlation was established. The ETa values obtained for the three time periods was used to analyse water use patterns across the basin thus giving insights on the underlying factors impacting on the water resources of the basin and hence facilitating the formulation of appropriate water resources management strategies for the basin.
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Book Section biblioteca |
| Language: | English |
| Published: |
International Society for Photogrammetry and Remote Sensing
2008
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| Subjects: | Environmental effects, Water balance, Water use, Remote sensing, Energy balance, Heat transfer, |
| Online Access: | http://hdl.handle.net/1834/7329 |
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| Summary: | Actual Evapotranspiration (ETa) is one of the most useful indicators to explain whether the water is being used as “intended”. ETa variations, both in space and time and from different land use types are seen to be highly indicative for the adequacy, reliability and equity in water use; the knowledge of these terms is essential for judicious water resources management. Unfortunately, ETa estimation under actual field conditions is still a big challenge to both scientists and water managers. The complexity associated with the estimation of ETa has lead to the development of various methodological approaches for estimating it over time. During the last two to three decades, significant progress has been made to estimate actual evapotranspiration using satellite remote sensing These methods provide a powerful means to compute ETa from pixel to the entire basin scale. In this study, Surface Energy Balance Algorithm for Land (SEBAL) was used to compute a complete radiation and energy balance along with the resistances for momentum, heat and water vapour transport for each pixel and then applied to assess the ETa at the basin scale and subsequently carryout a simple water balance for the basin. This was done for the Upper Ewaso Ng’iro North River Basin, in Kenya. Landcover/landuse for 2000, 2003 and 2006 were assessed and compared with ETa for the same periods and a significant correlation was established. The ETa values obtained for the three time periods was used to analyse water use patterns across the basin thus giving insights on the underlying factors impacting on the water resources of the basin and hence facilitating the formulation of appropriate water resources management strategies for the basin. |
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