Assessment of suspended solids in the Guadalquivir estuary using new DEIMOS-1 medium spatial resolution imagery

Abstract

Measurements of Total Suspended concentrations (TSS) are critical for monitoring geomorphological processes as well as ensuring the “good status” of transitional and coastal waters. Here, we explore the potential of the new DEIMOS-1, multi-spectral, medium-resolution satellite sensor for quantifying TSS dynamics within the large, turbid Guadalquivir estuary (SW Iberian Peninsula). Eight scenes were atmospherically corrected using various image-based procedures (apparent reflectance; Dark Object Subtraction, DOS; and solar zenith angle approximation, COSTZ). In-situ measurements (100 to 1400mgL−1) from three campaigns coinciding (±15min) with satellite overpasses were used to assess the semi-analytical algorithm from Nechad et al. (2010) relating water-leaving reflectance (ρw) to TSS. All bands were very sensitive to TSS, however saturation of the visible wavelengths was observed at the highest sediment loads. The best correlation was obtained for the NIR band (755–906nm) using the simple band-reflectance model at the top of atmosphere reflectance (ρw(TOA)), TSS (mgL−1)=21428.77 ρw(TOA)/(1−ρw(TOA)/0.21)−346.17 (r2=0.864, p<0.001, εr=25.411%, n=53), which was used to generate maps. This approach revealed detailed spatio-temporal variability in sediment concentrations within the river plume, near to shore and far up the river channel. We demonstrate that DEIMOS-1 has a high capability as a valuable tool for the frequent, synoptic monitoring of water-quality parameters needed for the optimum management of coastal and transitional waters.