Nitrogen loading and natural pressures on the water quality of a shallow Mediterranean lake.

The water quality of Koumoundourou Lake, a heavily modified, peri-urban, brackish and shallow lake near Athens, Greece, is under multiple stressors due to the industrial activities in the catchment area and natural pollution pressures. Although the broader area has undergone significant land use changes since the beginning of the 20th century converting it from rural to heavily industrialized, Koumoundourou Lake remained as one of the few habitats in Attica Region, for large numbers of aquatic birds. The water quality of the lake has been recently improved, which contributed to the increase of aquatic birds' population in the area and to the higher, in relation to the past, nitrogen inputs from natural sources. Therefore, a monitoring program has been implemented to assess the pollution pressure factors in the lake. A water quality model has been also used to simulate the lake's processes and estimate the nutrient mass budget focusing on the various nitrogen loading mechanisms (natural and anthropogenic). Based on the model output, the main polluting factor of the lake is the groundwater inflows. Aquatic birds affect slightly the lake's water quality, while the dry and wet atmospheric deposition contributes insignificantly to the total nitrogen loading.

Historical trends and the long-term changes of the hydrological cycle components in a Mediterranean river basin.

Identifying the historical hydrometeorological trends in a river basin is necessary for understanding the dominant interactions between climate, human activities and local hydromorphological conditions. Estimating the hydrological reference conditions in a river is also crucial for estimating accurately the impacts from human water related activities and design appropriate water management schemes. In this effort, the output of a regional past climate model was used, covering the period from 1660 to 1990, in combination with a dynamic, spatially distributed, hydrologic model to estimate the past and recent trends in the main hydrologic parameters such as overland flow, water storages and evapotranspiration, in a Mediterranean river basin. The simulated past hydrologic conditions (1660-1960) were compared with the current hydrologic regime (1960-1990), to assess the magnitude of human and natural impacts on the identified hydrologic trends. The hydrological components of the recent period of 2008-2016 were also examined in relation to the impact of human activities. The estimated long-term trends of the hydrologic parameters were partially assigned to varying atmospheric forcing due to volcanic activity combined with spontaneous meteorological fluctuations.