Estudo de aquíferos fraturados e porosos com base em deteção remota em Wako Kungo, Angola

A água subterrânea em Angola é usada como água de abastecimento para várias áreas urbanas e é também uma importante fonte de abastecimento de água rural e para a agricultura. Com a crescente procura de água, estudos anteriores relacionados com o uso de deteção remota e SIGs no mapeamento de águas subterrâneas podem mostrar-se altamente úteis no desenvolvimento e gestão eficiente e controlada dos recursos hídricos subterrâneos

Flood Extent Mapping in the Caprivi Floodplain Using Sentinel-1 Time Series

Deployment of Sentinel-1 (S1) satellite constellation carrying a $C$-band synthetic aperture radar (SAR) enables regular and timely monitoring of floods from their onset until returning to nonflooded (NF) conditions. The major constraint on using SAR for near-real-time (NRT) flood mapping has been the inability to rapidly process the obtained imagery into reliable flood maps. This study evaluates the efficacy of S1 time series for quantifying and characterizing inundation extents in vegetated environments. A novel algorithm based on statistical time-series modeling of flooded (F) and NF pixels is proposed for NRT flood monitoring. For each new available S1 image, the probability of temporarily F conditions is tested against that of NF conditions by means of likelihood ratio tests. The likelihoods for the two conditions are derived from early acquisitions in the time series. The algorithm calibration consists of adjusting two likelihood ratio thresholds to match the reference F area extent during a single flood season. The proposed algorithm is applied to the Caprivi region, the resulting maps were compared to cloud-free Landsat-8 (LS8) derived maps captured during two flood events. A good spatial agreement (85–87%) between LS8 and S1 flood maps was observed during the flood peak in both 2017 and 2018 seasons. Significant discrepancies were noted during the flood expansion and recession phases, mainly due to different sensitivities of the data sources to the emerging vegetation. Overall, the analysis shows that S1 can stand as an effective standalone or gap-filling alternative to optical imagery during a flood event

Assessing groundwater storage changes using remote sensing - based evapotranspiration and precipitation at a large semiarid basin scale

A method is presented that uses remote sensing (RS)-based evapotranspiration (ET) and precipitation estimates with improved accuracies under semiarid conditions to quantify a spatially distributed water balance, for analyzing groundwater storage changes due to supplementary water uses. The method is tested for the semiarid Konya basin (Turkey), one of the largest endorheic basins in the world. Based on the spatially distributed water balance estimation, the mean irrigation for croplands was 308 mm yr−1, which corresponds to a total reduction of 2270 million cubic meters per year (106 m3 yr−1, or MCM yr−1) in the groundwater storage during the study period 2005–09. The storage change estimated as the residual of the spatially distributed water balance was confirmed by the volume change calculated from groundwater table observations. To obtain an improved precipitation distribution, the monthly Tropical Rainfall Measuring Mission (TRMM) rainfall product was assessed. After a bias removal, TRMM data were combined with the snow water equivalent estimated by a multivariate analysis using snow gauge observations, the Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover product, and the digital elevation model. With respect to the distribution of ET, the standard SEBS and the soil moisture integrated SEBS-SM models were compared; SEBS-SM proved to better reflect the water-limited evapotranspiration regime of semiarid regions. The RS-based distributed water balance calculation as presented in this study can be applied in other large basins, especially in semiarid and arid regions. It is capable of estimating spatially distributed water balances and storage changes, which otherwise, by ground-based point measurements, would not be feasibl