Finding options to improve catchment water quality—Lessons learned from historical land use situations in a Mediterranean catchment in Slovenia

The main objective of this study is to investigate the impact of the historical land use situations on the river water quality under present climate and land management conditions and what can be lessons learned from it. The historical land use situations are based on digitised historical maps of existing past land use cover distribution of small Slovenian catchment (River Reka) from 1787, 1827, 1940 and 1984. Maps were compared between each other and baseline land use situation in 2009. The well-known river basin model SWAT was used to simulate the influences of land use situations on water quality, especially in terms of suspended sediments concentration. Results indicate that the historical land use situations would decrease water quality. Lessons learned from the study are as follows: (1) based on the more than 200-year-wide research time window, we can state that vineyards and orchards are preferred agricultural land use with undesired side effect on water quality; (2) climate, terrain characteristics and wine demand on the market are the driving factors for the land use pattern – share of vineyards remains fairly constant through the years, regardless of changes in authorities; (3) historical land use patterns would, in present times, cause an increased occurrence of erosion and deterioration of environmental conditions for organisms in surface waters; and (4) the present land use pattern with regard to the observed sediment concentration is still not an optimal solution. Further land use adjustments or agri-environmental measures are required to achieve water quality improvements. Historical examples can serve as lessons learned for the future with the purpose of minimising the influences of planned land use changes on water resource quality and quantity.