The impact of artificial drainage on water quality in two model areas in the bohemian forest foothills

This contribution arises from a broader research assignment dealing with the changes in soil properties and characteristics which have occurred following the artificial drainage of some agricultural soils in the Czech Republic. The current state is statistically compared with the state before the drainage. Thanks to the Research Institute for Soil and Water Conservation database, extensive sets of historical data are available. To enable a more detailed evaluation of the changes discovered, we chose two smaller study areas with different soil use. In the first area (Haklovy Dvory – arable land) there is intensive use of the soil, while in the other area (Železná – pastures) the use is not intensive. Historical data from about 30 years ago on the quality of surface and ground (well) water in the Železná area were taken as a starting point. The same types of water quality analyses were then made with water samples taken semi-annually in the Železná area since 2004 and once only (in 2005) in the Haklovy Dvory area. That led to the creation of an extensive body of information of water quality in the study areas. Within the framework of this information, the recent data, being still constantly supplemented, and the historical data on tile drainage, surface (stream) and underground (well) water quality are compared. In the course of the monitoring we focused on the following chemical indicators in the water: pH, alkalinity-acidity, total hardness, the concentrations of selected cations (magnesium, calcium, potassium, ammonia) and most important anions (bicarbonates, nitrates, nitrites, sulphates, phosphates, chlorides) and the electrical conductivity of the water. Individual samplings of surface and tile drainage water were, on the basis of the above mentioned analytical data, assigned appropriate quality categories according to the five-level pollution classification system defined by surface water quality standard (ČSN 75 7221). In Železná, no pronounced water pollution was found during the entire course of the monitoring, with the exception of one sampling point in the vicinity of which there was once a farmyard manure heap. By contrast, in the intensively managed Haklovy Dvory study area there was evidence of significant pollution of all tile drainage water samples. This finding supports our hypothesis about a direct impact of the type of agriculture practised in the area on the quality of tile drainage water. Both the use of fertilizers for agricultural crops and the intensive tillage of the soil have a commensurately large negative impact on the quality of tile drainage water and, subsequently, on the quality of water in surface watercourses.