engleski

Anthropogenic influences on a karst island, the Blato aquifer on the island of Korčula, Croatia

The Blato aquifer on the island of Korčula has two major threats to the quality of its potable water a) salt water intrusion and b) agricultural diffuse groundwater pollution. To assess the possible impact of land-use change on groundwater a detailed study of both the aquifer and soil cover in this unique karst system were carried out. The soil geochemistry was used to determine the present state of the soil cover and the soil profile related to agricultural practices and their changes during the past one hundred years. The studied catchment is located in the most western part of the island Korčula, about 1, 3 km away from the sea. The Blatsko polje covers about 3 km2, and the area of hydrogeological catchment is 28, 4 km2. The area is mostly covered by antropogenic soils, rendzinas, terra rossa, and brown soils on limestones. During the past, waters often flooded larger parts of polje during autumn-winter period, sometimes even covered parts of polje for several years. At that time, polje was used to grow short period crops like millet, or as pastures. Terraces on surrounding hills were used to grow olives, vineyards and figs. Melioration of Polje begun at 1912, when the 2000m tunnel was created from the lowest point of the Polje to the Bristva cove at the northern part of the island. After the hydromelioration was complete, vineyards were gradually relocated to Polje.. Intensive farming is detected as a potential source of pollution of soils, surface and underground water. The most often pollution comes from nitrates and pesticides, but also from accumulation of heavy metals. The abstraction wells are located in an agricultural area, so special care is needed in application of fertilizers, pesticides, herbicides and fungicides.

Karst aquifer; diffuse pollution; arable soil; land-use; climate change.

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