NDVI sensitivity to the hydrological regime in semiarid mountainous environments

This work shows the sensitivity of NDVI as an indicator of the global hydrological regime of the year. The annual water balance in the area was simulated through a physically-based distributed hydrological model previously calibrated and validated in the area from 2001 till 2010. NDVI was obtained from Landsat TM at the end of the dry season in 1000 points randomly distributed over a pine cover in a mountainous Mediterranean area. The influence of different hydrological processes related to the water balance in the soil on the NDVI values was analyzed through Pearson correlation matrices and Principal Components Analyses. Results showed that the NDVI was particularly sensitive to the regime of annual variables related to the snow layer dynamics, especially to snowmelt. These relationships were quantified, with the best fit being obtained between NDVI and the dimensionless index snowmelt divided by precipitation (R2 around 0.7). The adjustments obtained could, in the future, constitute a tool for the estimation of hydrological variables from satellite data in data-poor situations conditioned by the commonly steep slopes and difficult access in mountainous areas.

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