No abstract

Three District Water Authorities cover the whole Hungarian stretch of the Danube. Since the formation of the monitoring network fifteen years ago, the water quality has been observed at fifteen sampling points. Throughout this time, sampling has been performed under different hydrometeorological conditions. Based on these investigations, it was found that the quality of the river was influenced equally by the local and the hydrometeorological conditions. Major pollution sources are: the sewage from Bratislava, Györ and Budapest; the paper pulp, chemical, and sugar beet factories in the Slovakian catchment; the Hungarian chemical, petro-chemical, and food industries; and non-point source pollution from agriculture. The effects of these sources depend on the degree of wastewater treatment, and on the mixing rate. The waste loads provide a continuous source of nutrients, giving rise to bacterial proliferation. The organic nitrate and phosphorus loads are increasing, which is compensated for by biodegradation. In the winter, when the water temperature falls below 10°C and solar radiation is low, saprobic conditions characterize the water quality. In the summer, when solar radiation and temperature increase, trophic conditions determine the water quality. Thus, in winter the ammonia content increases, but in the spring, nitrification starts to improve and, especially in the lower reaches, algal overproduction can be detected. This situation changes during flood periods, when the concentration of polluting material is decreased by dilution, and at the same time, the high level of suspended solids inhibits the growth of organisms needing solar radiation. The most unfavourable water quality conditions occur in the winter low-flow period, when problems may occur in drinking water supply if the water is chlorinated.

No abstract

Population growth and higher living standards have resulted in ever-increasing demand for water. For the present study natural recharge was computed from a water balance model and daily water level fluctuations were measured to study the increase in water level due to artificial recharge. Numerical models were developed using MODFLOW to analyze the feasibility of different artificial recharge arrangements such as check dam and percolation pond with percolation wells individually and in combination and evaluate the effectiveness of the structures in recharging the aquifer. The maximum increase in water level was found to be 3.46 m, 2.54 m and 4.7 m respectively for the check dam, percolation pond with three percolation wells and combined structure arrangement after 2 years of artificial recharge. The zone of influence was obtained as 400 m, 600 m and 500 m respectively for the check dam, percolation pond and combined structure system. Water level fluctuations also proved the same. Water level increase obtained from the natural recharge study was only of the order of 0.2 m. Artificial recharge is found to be very effective for sustainable development of water resources and the percolation pond was found to be the most appropriate structure for groundwater recharge for the study area.

No abstract