ABSTRACT

Trichonis Lake catchment covers a semi-mountainous area of 403km2 including the largest in volume greek lake (2.6×l09 m3 with ~100km2 of surface area) located in western Greece. It is an area of complex geology, highly tectonized, with many different rock formations and hydrogeologic properties. In addition the hydrological regime has significantly changed over the years especially as a result of human intervention. Particularly the construction of a sluice gate in 1957, which conveys water to another lake catchment for irrigation and flood prevention purposes, has resulted in the lake water level drop of about 2m. It is also an area of high ecological value since calcareous fens around the shore of the lake are important habitats with rare species which need a stable environment to survive. The purpose of this study is to compare the hydrology of the area before and after the application of the regulating structure in terms of water balance, land use and climate changes. A physically-based distributed model (MIKE-SHE) was set up and calibrated for two periods: 1955-1957 and 1990-1992. Changes in land use, particularly forest to agricultural/irrigated land have been identified by comparing old air-photographs in GIS with current land uses and were also incorporated in the model. The results show lower values of actual evaporation and évapotranspiration for the latter period as a result of lower values of precipitation, temperature and wind velocity. The model may potentially be used as a platform for water management scenarios. For instance a future scenario will be constructed based on the existing models in order to assess the relative impact a climate change (in terms of temperature and rainfall) would have in the future. Also the model may also be used to simulate past hydrological state of Trichonis lake catchment if the required data is available.