Ecological status assessment of Pikrodafni stream (Attica, Greece), restoration and management measures

Abstract

During the last decade, the need for protection and restoration of urban streams has gained international recognition. Pikrodafni stream is one of the few remaining streams of Athens, Greece, which despite being subject to significant pressures, such as destruction of its riparian zone and illegal sewage disposal, still retains some of its important hydromorphological and biological characteristics. The objectives of this study aim toward (a) the identification of the most important pollution pressures, (b) the understanding of the dominant eco-hydrological processes of the stream, and (c) the design of efficient protection and restoration measures. For this purpose, a large number of environmental parameters (physicochemical, nutrients, microbiological, and biological components) at key points along the stream were monitored and analyzed at a monthly basis for a year. The results indicated heavy pollution pressures throughout the basin attributed to illegal sewage and garbage disposal. High concentration levels of nitrate, nitrites, ammonia, total coliforms, and dissolved oxygen were detected particularly at the lower reaches, and water quality was ranged from poor to moderate. Poor habitat biodiversity was also observed accompanied by the dominance of invasive plant species and illegal constructions covering most of the riparian zone. Based on the results of this study, the following conservation and management measures were initiated: (1) removal of certain invasive species and the planting of native vegetation, (2) establishment of a continuous monitoring water quality program at key points, where the most significant pollution sources are identified, accompanied by heavy penalties to the polluters, (3) erosion defense constructions to specific parts of the embankments by using bio-engineering techniques, and (4) removal of some of the existent flood control constructions from the streambed, which prevent fishes to move upstream. These measures are proposed within the context of the EU Water Framework Directive and imply the constant water monitoring and management in order to assess and adjust them appropriately, so as to achieve good ecological status.