THE USE OF WATER QUALITY INDICES (WQI AND SAR) FOR MULTIPURPOSE ASSESSMENT OF WATER IN DAM RESERVOIRS

The paper intends to show the potential of diverse benefits of two water quality indices used to assess 4 dammed lakes in lowland area in NE Poland: the Water Quality Index (WQI), developed by the Scottish Development Department, used in the assessment of water potential for human consumption, fisheries, industries and recreation, as well as the Sodium Adsorption Ratio (SAR), recommended by the Salinity Laboratory of the US Department of Agriculture, used in the water assessment for the irrigation purpose. Our study was based on the results of a water quality monitoring programme, in which the following water parameters have been analyzed: pH, dissolved oxygen, electrical conductivity, biological oxygen demand, chemical oxygen demand, NH4+, NO3-, Cl-, SO42-, Na+, Ca2+, Mg2+ and HCO3-. The water quality parameters differed among the studied reservoirs, and represented a medium (Wykrot) and poor class (Grodzisk Duzy, Karwacz and Loje) on a 5-degree WQI scale. The SAR was less diversified and water in the studied reservoirs showed class I. The results revealed that the water in all the reservoirs is suitable for irrigation with no hazard to the soil structure as well as for breeding of fish that tolerate lower water aeration. This water can be also used for recreational purposes, although direct contact with water is not recommended. The water quality indices (WQI and SAR) showed a great potential in the assessment of water for multi-purpose usage. The WQI and SAR are excellent tools for summarizing overall water quality conditions over space and time. When used together, they are also a method of providing relevant information for specific water use that can be more readable for planners and managers.