Abstract:
Fragmented ecosystems of the desiccated Aral Sea seek answers to the profound local
hydrologically- and water-related problems. Particularly, in the Small Aral Sea Basin
(SASB), these problems are associated with low precipitation, increased temperature,
land use and evapotranspiration (ET) changes. Here, the utility of high-resolution satellite
dataset is employed to model the growing season dynamic of near-surface fluxes controlled
by the advective effects of desert and oasis ecosystems in the SASB. This study adapted and
applied the sensible heat flux calibration mechanism of Surface Energy Balance Algorithm
for Land (SEBAL) to 16 clear-sky Landsat 7 ETM+ dataset, following a guided automatic
pixels search from surface temperature Ts and Normalized Difference Vegetation Index
NDVI (Tshot=NDVI ; Tscold=NDVI ). Results were comprehensively validated with flux components
and actual ET (ETa) outputs of Eddy Covariance (EC) and Meteorological Station (KZL)
observations located in the desert and oasis, respectively. Compared with the original
SEBAL, a noteworthy enhancement of flux estimations was achieved as follows: – desert
ecosystem ETa ! R2 = 0.94; oasis ecosystem ETa ! R2 = 0.98 (P < 0.05). The
improvement uncovered the exact land use contributions to ETa variability, with average
estimates ranging from 1.24 mm d 1to 6.98 mm d 1. Additionally, instantaneous ET to
NDVI (ETins-NDVI) ratio indicated that desert and oasis consumptive water use vary
significantly with time of the season. This study indicates the possibility of continuous
daily ET monitoring with considerable implications for improving water resources decision
support over complex data-scarce drylands
