Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation
<p>A portion of globally generated surface and groundwater resources evaporates from wetlands, waterbodies and irrigated areas. This secondary evaporation of <q>blue</q> water directly affects the remaining water resources available for ecosystems and human use. At the global sc...
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doaj-d5a3535b5dd84f3ca98b0b0eb52ccbee2020-11-25T01:08:00ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382018-09-01224959498010.5194/hess-22-4959-2018Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilationA. I. J. M. van Dijk0J. Schellekens1J. Schellekens2M. Yebra3H. E. Beck4L. J. Renzullo5A. Weerts6A. Weerts7G. Donchyts8Fenner School of Environment & Society, Australian National University, Canberra, ACT, AustraliaDeltares, Delft, Boussinesqweg 1, 2629 HV Delft, The NetherlandsVandersat B.V., Wilhelminastraat 43a, 2011 VK, Haarlem, The NetherlandsFenner School of Environment & Society, Australian National University, Canberra, ACT, AustraliaDepartment of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USAFenner School of Environment & Society, Australian National University, Canberra, ACT, AustraliaDeltares, Delft, Boussinesqweg 1, 2629 HV Delft, The NetherlandsHydrology and Quantitative Water Management group, Wageningen University & Research, Wageningen, The NetherlandsDeltares, Delft, Boussinesqweg 1, 2629 HV Delft, The Netherlands<p>A portion of globally generated surface and groundwater resources evaporates from wetlands, waterbodies and irrigated areas. This secondary evaporation of <q>blue</q> water directly affects the remaining water resources available for ecosystems and human use. At the global scale, a lack of detailed water balance studies and direct observations limits our understanding of the magnitude and spatial and temporal distribution of secondary evaporation. Here, we propose a methodology to assimilate satellite-derived information into the landscape hydrological model W3 at an unprecedented 0.05°, or ca. 5 km resolution globally. The assimilated data are all derived from MODIS observations, including surface water extent, surface albedo, vegetation cover, leaf area index, canopy conductance and land surface temperature (LST). The information from these products is imparted on the model in a simple but efficient manner, through a combination of direct insertion of the surface water extent, an evaporation flux adjustment based on LST and parameter nudging for the other observations. The resulting water balance estimates were evaluated against river basin discharge records and the water balance of closed basins and demonstrably improved water balance estimates compared to ignoring secondary evaporation (e.g., bias improved from +38 to +2 mm yr<sup>−1</sup>). The evaporation estimates derived from assimilation were combined with global mapping of irrigation crops to derive a minimum estimate of irrigation water requirements (<i>I</i><sub>0</sub>), representative of optimal irrigation efficiency. Our <i>I</i><sub>0</sub> estimates were lower than published country-level estimates of irrigation water use produced by alternative estimation methods, for reasons that are discussed. We estimate that 16 % of globally generated water resources evaporate before reaching the oceans, enhancing total terrestrial evaporation by 6.1×10<sup>12</sup> m<sup>3</sup> yr<sup>−1</sup> or 8.8 %. Of this volume, 5 % is evaporated from irrigation areas, 58 % from terrestrial waterbodies and 37 % from other surfaces. Model-data assimilation at even higher spatial resolutions can achieve a further reduction in uncertainty but will require more accurate and detailed mapping of surface water dynamics and areas equipped for irrigation.</p>https://www.hydrol-earth-syst-sci.net/22/4959/2018/hess-22-4959-2018.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
A. I. J. M. van Dijk J. Schellekens J. Schellekens M. Yebra H. E. Beck L. J. Renzullo A. Weerts A. Weerts G. Donchyts |
spellingShingle |
A. I. J. M. van Dijk J. Schellekens J. Schellekens M. Yebra H. E. Beck L. J. Renzullo A. Weerts A. Weerts G. Donchyts Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation Hydrology and Earth System Sciences |
author_facet |
A. I. J. M. van Dijk J. Schellekens J. Schellekens M. Yebra H. E. Beck L. J. Renzullo A. Weerts A. Weerts G. Donchyts |
author_sort |
A. I. J. M. van Dijk |
title |
Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation |
title_short |
Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation |
title_full |
Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation |
title_fullStr |
Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation |
title_full_unstemmed |
Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation |
title_sort |
global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation |
publisher |
Copernicus Publications |
series |
Hydrology and Earth System Sciences |
issn |
1027-5606 1607-7938 |
publishDate |
2018-09-01 |
description |
<p>A portion of globally generated surface and groundwater resources evaporates
from wetlands, waterbodies and irrigated areas. This secondary evaporation
of <q>blue</q> water directly affects the remaining water resources available
for ecosystems and human use. At the global scale, a lack of detailed water
balance studies and direct observations limits our understanding of the
magnitude and spatial and temporal distribution of secondary evaporation.
Here, we propose a methodology to assimilate satellite-derived information
into the landscape hydrological model W3 at an unprecedented 0.05°, or
ca. 5 km resolution globally. The assimilated data are all derived from
MODIS observations, including surface water extent, surface albedo,
vegetation cover, leaf area index, canopy conductance and land surface
temperature (LST). The information from these products is imparted on the
model in a simple but efficient manner, through a combination of direct
insertion of the surface water extent, an evaporation flux adjustment based on LST
and parameter nudging for the other observations. The resulting water balance
estimates were evaluated against river basin discharge records and the water
balance of closed basins and demonstrably improved water balance estimates
compared to ignoring secondary evaporation (e.g., bias improved from +38 to
+2 mm yr<sup>−1</sup>). The evaporation estimates
derived from assimilation were combined with global mapping of irrigation
crops to derive a minimum estimate of irrigation water requirements
(<i>I</i><sub>0</sub>), representative of optimal irrigation efficiency. Our <i>I</i><sub>0</sub>
estimates were lower than published country-level estimates of irrigation
water use produced by alternative estimation methods, for reasons that are
discussed. We estimate that 16 % of globally generated water resources
evaporate before reaching the oceans, enhancing total terrestrial evaporation
by 6.1×10<sup>12</sup> m<sup>3</sup> yr<sup>−1</sup> or 8.8 %. Of this volume,
5 % is evaporated from irrigation areas, 58 % from terrestrial waterbodies and 37 % from other surfaces. Model-data assimilation at even
higher spatial resolutions can achieve a further reduction in uncertainty but
will require more accurate and detailed mapping of surface water dynamics and
areas equipped for irrigation.</p> |
url |
https://www.hydrol-earth-syst-sci.net/22/4959/2018/hess-22-4959-2018.pdf |
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