The study area of the Nida valley was examined to investigate variations in groundwater and surface water levels, as well as the interaction between them. In the valley, there were three branches. The two actives were the Nida River itself and the Smuga Umianowicka branch while the Stara Nida branch was dry during the measurement session. Over a 12-month period from June 2021 to June 2022, 7 monitoring points were equipped with piezometers, comprising 5 groundwater points and 2 surface water points. The monitoring frequency was set to 30 minutes. The results of this research indicate that there are significant differences in the water level at the same observed point at different times. This study demonstrates seasonal changes in both surface water and groundwater levels with higher levels in autumn and winter and lower levels in spring and summer, which are closely tied to the changes in meteorological conditions during the research period, such as precipitation and air temperature. The study results also indicate that during summer and winter at the Nida River and its riparian area, losing stream is the primary process occurring in the studied reach. Conversely, during autumn and spring, the main process is gaining stream. At the human-maintained Smuga Umianowicka branch and in its riparian area, losing stream is the main process during summer and autumn, and gaining stream is the main process during spring. During winter, losing stream and gaining stream processes can occur simultaneously, and neither process takes place mainly.

Faced with the challenges of sustainable groundwater resource management in the arid zone, the identification of re-serves and their monitoring have become vital. This paper aims to identify the Turonian aquifer in the Cretaceous Béchar basin, and calculate its transmissivity, permeability and storage coefficient, as well as its evolution over time. This Tu-ronian aquifer is characterized by marine limestones (gentle dip shelters 45° to the North and 5° to 10° to the South). Pumping tests revealed a transmissivity T of 10–4 to 10–2 m2·s–1, a permeability K of 10–6 to 10–4 m·s–1 and a storage coeffi-cient S of approximately 10–3. Two piezometric campaigns, carried out between (1976–2018), show a converging and con-stant flow direction from the North–East to the South–West and from the North–West to the South–East towards the outlet of the basin. Decreased values were observed in the North and South–West borders due to isopiezometric lines. However, this water table is not in a stationary state, it shows seasonal and interannual fluctuations in relation to the variable rainfall and the exploitation rate. In terms of facies, the projection of the two hydrochemical campaigns, during 1976 and 2018 on the Piper diagram, did not show any significant evolution, they are concentrated in the chlorinated and sulphated calcium and magnesium facies.