The artificial infiltration process essentially replicates natural filtration, and requires high-quality raw surface water together with a suitable geological environment. A tilting weir gate with an intake structure was built to take off water from the Jizera River, and from there it passes through screens to a pumping station, which sends it on to the water treatment plant. Here it receives only basic mechanical pre-treatment using rapid sand filters before being pumped into infiltration basins, where the water takes about a day to soak down into the underlying aquifer.
Around Káraný there are 15 of these basins, which are 10-30 m wide, 2.5 m deep and between 100 and 500 m long. In total, they cover an area of seven hectares and provide 700-900 l/s of drinking water. The bottom of these basins is composed of a gravel-sand mixture from a nearby sand quarry, and once a year a 5 cm layer of sand is removed from them to restore their infiltration capacity. The treated water percolates down through the gravel layer in these basins and the underground rock environment, and in the process acquires the greater hardness and lower temperature typical of groundwater. It is then abstracted via wells connected together by siphons.
At the Káraný Water Treatment Plant, drinking water from all three of these sources is mixed, disinfected for supply using chlorine, and sent on its way to consumers through three discharge lines. Discharge lines I and II are connected to the reservoir tank at Flora and discharge line III goes to the Ládví reservoir.
In the 1950s, the issue of the shortage of drinking water arose again, and water managers were faced with a decision – whether to increase the production capacity of the existing sources or build new ones. The favourable geological character of the Káraný region attracted their interest again, and this time they made use of it in a way less conventional, innovative in its day. They decided to use its thick layers of gravel and sand to filter the water they abstracted from the Jizera River, and this technique allowed them to recharge the existing groundwater reserves.
...the total length of all 15 infiltration basins is 5.5 km?
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