engleski

Groundwater Problems of the Agricultural Region in Drava River Basin

In the begimning of the century the main problem of agriculture in Croatia was the excess of water. The crops were suffered from the high water table during the spring time, and harvest was hardly possible in the autumn. Heavy machinery were subsidizing the soil due to the working in the wet conditions. A great efforts and investments were done on the regulation works on the rivers, surface and subsurface drainage. Also, a number of accumulations were built for preventing floods. In the second phase (about thirty years ago), few locations for drainage testing were established in order to observe fluctuations of groundwater in reclaimed agricultural land. During the period from 1992 to 1996, the serious investigations were undertaken on the several experimental plots. Besides the other tasks, observations of ground water quantity and quality were under consideration. In that period we had few very dry years, but the last two, 1995 and 1996 had a rather significant quantity of precipitation, and what is much more important, snow. Variations of evapotranspiration in the analysed period were very small. The observations of groundwater fluctuation show that, in the controlled (drained) conditions, groundwater level rises up to about 0.6 m below surface in the winter period and drops below 2.0 m in the summer. The excess water is drained through the subsurface drainage which is functioning during the winter periods. Last two rainy years were reflected on drain discharge, but there effects on the groundwater level were not significant. Problem of the shortage is expressed during the mid – season (June – August) when the evapotranspiration is high, groundwater table deep and soil moisture content very small. The second problem which appears recently is soil and water pollution due to the intensive agricultural production. The ground water quality becomes very important in the most of developed countries. Protective chemicals and fertilizers are intensively used what is unexceptable from the standpoint of human ecology and nutrition. In the period of observation from 1992 to 1996 the concetrations of nitrates, herbicides (triazin), pesticides and heavy metals (copper, manganese, lead, zinc and cadmium) were measured in the soil, groundwater, drainage water and adjacent surface water courses. The results show that some of these parameters exceeds the upper limits of allowed values according to national and international regulations. Thus, the problem of ground waterquantity becomes significant as much as the problem of its quantity.

drainage; groundwater; effect; soil; ecology; water; fluctuation; heavy metals

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