Catchment-level water management plan for the Hietajärvi-Tuuslahti area

The objective of the thesis was to produce a catchment-level water management plan for Hietajärvi-Tuuslahti area. This was done by using spatial data and other information sources to describe the area, the water bodies, water characteristics and the loading factors. The study aimed to identify the main loading sources affecting the local water bodies and to propose measures that support the long- term maintenance of their good ecological status. A GIS-based two-phased index analysis approach was used to analyse the sub-catchments and to identify the priority areas where suitable water protection measures could be executed. Spatial datasets from national environmental authorities were used to analyse nutrient loading, land use, erosion sensitivity, hydrological conditions, and climate-related factors. The analysis was complemented by information gathered in a local discussion event, which provided insight into residents’ observations and interests regarding water management. The ecological state for both lakes is good but there have been signs of eutrophication. The study shows that the most significant human-induced loading in the area originates from agriculture, particularly around Lake Hietajärvi and between Hietajärvi and Tuuslahti. Additionally, in Tuuslahti area the runoff waters have an influence. Several sub-catchments were identified as priority areas where measures such as buffer zones, wetlands, and channel erosion control could effectively reduce nutrient loads and erosion. The results provide a basis for further planning and support the development of site-specific measures in cooperation with landowners.