engleski

Influence of climate changes on irrigation requirements in northen Croatia

With only 11.700 ha of irrigated agricultural areas, the Republic of Croatia holds one of the last positions in Europe. For this reason, the Government started the "Project of irrigation and management of agricultural land and waters", which will be implemented in three stages. A part of the Project was aimed at determining: Influence of climate changes on irrigation requirements in Northern Croatia ; Crop evapotranspiration (required amount of water) ; Soil water deficit ; Quality of irrigation water. Climate data of meteorological stations Đurđevac and Donji Miholjac, for the periods 1961- 2003 and 1994-2003 were used. Reference evapotranspiration (ETo) was calculated by the Penman-Monteith method, effective precipitation by the USBR method (US Bureau of Reclamation), while crop evapotranspiration (ETc) was calculated from the relationship between ETo and crop coefficient (Kc), taking account of the different stages of crop development. Soil water balance in luvisol was calculated for each crop using the Palmer method (corrected and calibrated according to Vidaček, 1981), for two different depths (to 0.1 m and 0.1-1.0 m). Investigations were carried out on soil of the following water constants: field water capacity (Fwc)=360 mm and wilting point (Wp)=160 mm. The following crops were tested: tobacco, soybean, sunflower, sugar beet, cabbage and kale, pepper, cucumber and tomato. Data were processed with the aid of the computer program "Cropwat". Quality of irrigation water was assessed for the County Canal watercourse ; water samples were taken in the period from 1983 to 2003. Water quality score was calculated for each year pursuant to the Water Classification Directive (Official Gazette 77/98). The following individual watercourse quality indicators were analyzed: oxygen concentration, oxygen saturation, COD (chemical oxygen demand) and BOD5 (biochemical oxygen demand). Of nutritious substances ammonium and nitrites were analyzed, while among microbiological indicators quality score was based on total coliform bacteria and the number of aerobic bacteria, as well as on the PB (Pantle-Buck) saporbic index. Research results revealed a rise in air temperature in the whole studied region in the last investigation period (1994-2003) – by 1 oC (Đurđevac) and by 0.6 oC (D. Miholjac). Due to higher air temperatures, water requirements of all crops (crop evapotranspiration) were increased in that period. Increased water requirements ranged from 22 mm in the Đurđevac region to 19.4 mm in the region of D. Miholjac (average over all crops). Water balance revealed also a higher water deficit in soil. Increased soil water deficit amounted to 8.9 mm in the Đurđevac region, and to 9.1 mm in the region of D. Miholjac (average over all crops). Water quality in the County Canal watercourse was monitored for 21 years, in 11 years of which water was above water category III according to group indicators. The results allow the conclusion that climate changes in the last investigation period caused increased water requirements of crops grown, and thereby also higher water deficit in soil and the need of providing larger quantities of good-quality irrigation water.

climate changes; irrigation requirements; water quality

Sažetak rada tiskan je u Knjizi sažetaka ; Beograd : National Committee of Serbia for the International hydrological programme of UNESCO ; str. 150-150 ; ISBN 86-80851-06-X.