Inland water resources are facing increasing quantitative and qualitative pressures, deriving from anthropogenic causes and the ongoing climate change. The monitoring of reservoirs is essential for sustainable management and preparation against water scarcity and extreme events, such as droughts. This research, relying on the Sentinel-2 and 3 missions, attempts to demonstrate the efficiency of combining remotely sensed water level and water area estimations, in order to estimate the water storage variation of Yliki reservoir. The case study is conducted in one of the few sufficiently monitored reservoirs in Greece, enabling a direct comparison of the proposed methodology results with in situ observations. Moreover, this research work proposes a weekly time interval for pairing level and area estimations, instead of shorter time intervals. The results strongly demonstrate the efficiency of remote sensing in the production of empirical level–area–storage (L–A–S) curves. Correlation to in situ monitored storage- and satellite-derived water level, area stand for 98.81% and 99.27% respectively. Water storage variation is estimated and compared to the observed time series, resulting in an RMSE of 1.28% of the reservoir capacity and a correlation of 96.14%. The empirical L–S relationship underestimates storage, while the A–S relationship overestimates storage when compared to the existing L–A–S curve.

Expected global climate change is allegedly becoming more intense, and the impacts on water resources are being tracked in various hydroclimatic regimes. The present research investigates a hydrologically important area of Greece, where four natural lakes are concentrated. It aims to quantify any potential long-term trends in lake water area, precipitation, and temperature timeseries. Water area timeseries spanning four decades are estimated by the mNDWI from Landsat satellite imagery and used as an index of each lake’s water storage. Precipitation and temperature measurements are obtained from the open access datasets Hydroscope and ERA5-Land, respectively. All of the timeseries were tested seasonally and annually with the Pettitt and Mann–Kendal tests for statistically significant breakpoints and trends detection. No timeseries analysis resulted in a statistically significant (at 0.05 or 0.1 levels) annual or seasonal trend. The hydroclimatic regime over the past forty years in western Greece is found to have been relatively stable. Land use was also assessed to have been relatively unchanging, converging to the overall stability of the local water regime. However, the findings of this research should not be interpreted as a reassurance against climate change, but as a call to further research for the detailed regional and local assessment of climate change and hydroclimatic variability with acknowledged statistical approaches.

The prolonged issues regarding the quantitative and qualitative characteristics of the water resources in the River Basin District of Thessaly (TRBD) have resulted in the environmental degradation and the reduction of the availability of water. Agriculture is the major water user, constituting up to 95% of total water demand. The pressures anticipated from the ongoing climate change are expected to cause further degradation, given the present status of the water resources. This research attempts to examine and quantify the water saving potential of TRBD, mainly for the agriculture sector, following the recommendations of the European legislation, the principles of sustainable development and environmental protection. Water saving tools are documented in several countries, including technical measures, such as drip irrigation systems and the modernization of the transfer networks, as well as deficit and scheduled irrigation practices and water reuse. These measures and practices are tested for their potential effect on water demand in TRBD, in addition to changing a portion of cotton cultivation areas to olive groves. To this end, the volume of irrigation demand is estimated at 2088×106, while total water demand stands for 2204×106. Afterwards the study proceeds to the evaluation of the water saving potential both independently and combined. The potential of water savings in TRBD is proven high, 14.3% of total water demand for technical measures, 10.7% if deficit irrigation is applied to specific crops, while it may reach 28.8% in case the measures are combined.