Uncontrolled groundwater abstraction for drinking water supply of Minsk city, Belarus has a negative impact on quantitative and chemical status of groundwater bodies and also on surface water ecosystems. Groundwater over-exploitation accelerates pollution of productive aquifers, causing increase of nitrogen concentrations in the main well fields used for central drinking water supply. For these reasons groundwater bodies around Minsk city are assigned the category at risk of not achieving good quantitative and chemical status.
Eleven well fields are established for domestic-industrial water supply of Minsk city with total number of inhabitants of over 2 million. Each of the well fields consists of dozens of exploitation wells of depth of 50-320 m. The oldest well fields (Novinki, Petrovschina, Zelionovka, and Drazhnia) were constructed between 1930-1950 and now are located within the territory of the city. Other well fields (Borovliany, Ostrovy, Volma, Vickovschina, Vodopoy, Felicianovo, and Zelenyj Bor) are located at the distance from eight to 25 km from the city in more favourable environmental surroundings.
Long-term intensive groundwater abstraction from the inter-moraine Dnieper-Sozh and Upper Proterozoic water-bearing complexes for the water supply of Minsk city has created a huge depression cone with the diameter of 40- 70 km and drawdown of groundwater levels of 20-30 m in the central part of the depression.
Groundwater exploitation is not only causing large-scale water level drawdowns but also reducing flows of small rivers around the Minsk city. Rivers are feeding depleted aquifers and losing their flow during the low-flow periods. This phenomenon in Minsk region was firstly noticed in 1974 when 7km of Volma River disappeared in summer time, 4 years after establishment of Volma well field, which was abstracting groundwater from Dnieper-Sozh water bearing complex. Now upstream flows of rivers Cna, Loshica, Slepianka, Volma, Trostianka and Sennica are impaired by exploitation of Minsk well fields.
Groundwater abstraction also accelerates pollution of productive aquifers. Well field Novinki is one of the oldest well fields in Minsk used for water supply since 1932. Groundwater monitoring reveals development of anthropogenic pollution of the aquifers mainly by nitrates. In 1932 nitrates were absent from the groundwaters of the well field but by 1970 concentrations of nitrates in a number of wells had reached 20–27 mg/l and in 1990 they had increased to 50–65 mg/l (European norm for drinking groundwater is 50 mg/l).
Results of field survey
Groundwater field survey was organised on 12-14 May 2014 with the purpose of detection of pollution in production wells of Novinki, Zelionovka, Vickovschina and Volma well fields. Three local groundwater experts and KE5 on groundwater of EPIRB project collected 19 groundwater samples for analysis of nutrients, heavy metals and organics. Field groundwater parameters (temperature, pH, electric conductivity and total dissolved solids) have been measured at the well. The aim of the field survey is to better learn reasons of groundwater contamination and propose measures for improvement of groundwater status.
Location of sampling points is presented in the figure 1. Results of field measurements are presented in the table 1 and results of laboratory analyses are presented in the table 2.
One can see from the table that nitrate concentrations are exceeding EU norm for drinking water (50 mg/l) in 6 sampled wells of Novinki well field and 1 sampled well of Zelionovka well field.
Fluorine concentration is exceeding drinking water norm (1,5 mg/l) in one well of Zelionovka well field and boron concentrations are slightly above the norm (1,0 mg/l) in one well of Novinki well field, one well of Zelionovka well field and one well of Vickovschina well field.
Iron concentrations are execeeding the EU norm (0,2 mg/l) up to 8 times in 3 wells of Vickovschina well field. Iron is not a toxic component. It is quite often detected in high concentrations due to specific hydrochemical characteristics of glacial aquifers and can be easily removed in the de-ironing facilities.
The reason and source of high nitrate concentration has to be detected, hovewer. It is assumed that nitrates are resulted by the long-term agricultural pollution around Novinki well field. Pilot project will be designed for the detecting of sources of nitrate pollution and development of programme of measures for its reduction.
- 2.4 Joint field surveys to cover the gaps
- Upper Dnieper River Basin