Integrating Radar Altimeters and Optical Imagery Data for Estimating Water Volume Variations in Lakes and Reservoirs (Case Study: Lake Nasser)

Abstract

Monitoring of variations in water for lakes and reservoirs is a requirement for meeting human needs and assessing ongoing climatic changes. However, regular gauging networks fail to provide the information needed for water volume data. The aim of this study is to evaluate an approach to estimate water volume variation for the southern part of Lake Nasser in Egypt without in-situ gauge measurements and bathymetry maps. Combination of both Hydroweb satellite altimetry and Landsat 8 satellite imagery data was used. As compared to in-situ water levels, satellite altimetry provided accurate water levels variations for Lake Nasser; the RMSE was 0.28 m, with excellent agreement (R 2 is 0.98). The lowest water level of altimetry database i.e. 174.57 m was used as a reference level for estimating water volumes variations for the study duration 8/2014-6/2015. All water altimetry levels were converted to differences of recorded water level above the lowest altimetry Level (∆WL). Series of Landsat 8 imagery data were selected to extract surface areas corresponding to radar altimetry water levels dates. Areas-∆WL relationship model was established as a polynomial function: A = f(∆WL), and therefore, the relationship of the water volume above the lowest water level for the study time (∆V) and ∆WL was obtained through the analytical integration of (Area-∆WL) model. Another approach (Heron method) was also applied for estimating water volume variations. Validation of these two approaches showed that estimated water volume variations above reference water level using both methods i.e. integration and Heron agreed well with in-situ measurements of volume variation deduced from recent bathymetry map and in-situ water levels (R 2 for both methods = . Another byproduct for these approaches was the modeling for a remote detecting water level. Once the F(L) relationship is set up for a given region, future Landsat images can be utilized to track water levels freely of radar altimetry. Finally it can be concluded that remote sensing resources (satellites radar altimeters and optical satellite images) that are openly accessible these days represent a great opportunity to remotely monitor reservoir water capacity and help in examining and observing hydrological and water driven procedures.

Bathymetric and Capacity Relationships Based on Sentinel-3 Mission Data for Aswan High Dam Lake, Egypt

“…An NRMSE value of approximately 12.8% was presented (Figure 13b), and also shows water volume variations over a time period from June 2016 to July 2019. The results are relatively similar to the results of Ebaid [27], who also applied the Heron method for the period from 2014 to 2015 to estimate water volume variations relative to reference water level for the southern part of AHDL in Egypt. She used available free Landsat and radar altimeter datasets with R 2 = 0.98 and RMSE values that were 13.2% of the mean volume variation.…”

“…In all these works, water level and water surface information were used to estimate stored water volumes, in combination with limited in situ data pertaining few different water levels. Ebaid [27] also applied the Heron method for the period from 2014 to 2015 to estimate water volume variations relative to reference water level for the southern part of AHDL in Egypt. She used available free Landsat and radar altimeter datasets with R 2 = 0.98, and RMSE values were 13.2% of the mean volume variation.…”

Study of Massive Floating Solar Panels over Lake Nasser

“…Knowledge of water temperature is important in estimating the efficiency of the FPV. Satellite's images were used to infer the surface water temperature [17]. It was found that the surface water temperature depends on the depth of water.…”

“…where W L is the average monthly water level [13]. Several studies were conducted using satellite remote sensing data to assess the changes in the water level [14,15] and water volume [16][17][18]. These studies helped as well in estimating the annual water loss by evaporation from the lake.…”