Water balance of Mediterranean karst soil in Bosnia and Herzegovina as a water conservation and erosion control factor

Abstract This research was carried out in the locality of Dubljani in Popovo Polje, which is one of a series of typical Dinaric karstic poljes situated within the Mediterranean part of Bosnia and Herzegovina. Previous research has shown that the Mediterranean part of Bosnia and Herzegovina has the largest surplus and deficit of water at the same time. Because of this, we wanted to explore how much of the water goes to drainage runoff, and then how slope affects the surface runoff. The ultimate goal was to find a way to conserve water and prevent erosion in these natural conditions. Precipitation, drainage runoff, surface runoff and soil erosion were measured at the agro-hydrological station during the experimental period with the goal of understanding the problem of water erosion intensity. In order to study the relationship between precipitation and drainage runoff, six lysimeters with different soil depths were installed (1.3 m, 1.0 m, 0.5 m, 0.3 m and one karst simulation). In addition, six metal cassettes were set up and filled with the same soil used by the lysimeters to simulate inclinations of 1, 5 and 10%, involving both bare and grass-covered soil (Lolium perenne L., Poa pratensis L., Festuca rubra var. fallax Thuill., Dactylis glomerata L., Trifolium repens L., Trifolium pratense L.), and the total water runoff and soil erosion were monitored. The results indicate large differences in the agro-hydrological budget between bare rocky soil and loamy-clayey soils of different depths. The drainage runoff coefficient during the first year ranged from 0.33 in deep soil to 0.50 in shallow soil, while in the second year it ranged from 0.38 to 0.58. The results of the drainage runoff coefficient for the bare karst was higher than 0.70 during both years. The results of the measurement of the total surface runoff and soil erosion indicate that the impact of inclination can be mitigated by grass cover. The surface runoff measurements during the 2 years for both bare and covered soil at the same inclinations show a reduction in the surface runoff from 32 to 86%. The reduction of erosion in covered soil compared to bare soil ranged from 55 to 75%in the first year, while in the second year, erosion in the covered soil was almost completely stopped (a reduction of > 95%). This study shows a huge impact of soil cover on the agrohydrological budget where runoff potential increases with soil depth. Moreover, the results confirm the role of vegetation role in reducing runoff and soil erosion, which is important for better conservation of moisture in the soil. In future research, attention should be paid to the seasonal character of erosional processes.