Figure 2
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Data sources:
Data was provided by the Ministry of Environment of the Republic of Armenia under the ENI SEIS II East project activities
(C10, C11) Water quality indicator, by observation points and years provided by ArmStatBank
Note: The data series are calculated as the average of annual mean ammonium concentration (NH4-N/l) for river sites in Armenia for the period 2008-2017. The number of river sites is 45 (21 sites above settlements and 24 sites below), representing 22 rivers. The right hand plots show the average time series without the site 55.
Biochemical oxygen demand (BOD) and ammonium are key indicators of organic pollution in water. BOD shows how much dissolved oxygen is consumed in the decomposition of organic matter present in water. Concentrations of these parameters normally increase as a result of organic pollution caused by discharges from wastewater treatment plants, industrial effluents and agricultural runoff. Severe organic pollution may lead to rapid de-oxygenation of river water, high concentration of ammonium and disappearance of fish and aquatic invertebrates. The main source of organic pollution in Armenia is non-treated or not sufficiently treated wastewater, which, due to the lack of treatment plants, is emitted to the river. There are only six treatment plants in Armenia, with mechanical treatment only.
The BOD and ammonium concentration have increased below settlements in the period 2011 to 2017, due to discharge of untreated domestic wastewater from settlements and agriculture run-off. Over the period 2008 to 2017 average BOD increased by 25% and average ammonium concentration by 74% for sites below settlements. Average BOD and ammonium concentration for river sites above settlements have remained more or less stable. This indicates that there are limited changes in activities causing emissions in the less populated areas. Across all sites, the increase from 2008 to 2017 was thus slightly less than for the sites below settlements (18% and 72% for BOD and ammonium concentration, respectively).
River Hrazdan is one of the longest and most polluted rivers in Armenia. The effect of the influence of untreated wastewater is obvious especially at the monitoring site 55, which is the nearest and most impacted site after Yerevan city, the capital of Armenia, with about 1 million inhabitants. This has a major impact on the average time series, especially for ammonium. In 2017, the average ammonium concentration at sites below settlements was two times higher when including monitoring site 55 and the difference between the averages with and without this site has increased over time. For BOD, the difference is less, but also here it has increased over time, meaning that the BOD has increased more at site 55 than at other sites. At the beginning of the time series the average of sites below settlements was around 5% lower when excluding site 55, while it was around 20% lower at the end of the time series. Excluding site 55 the increase from 2008 to 2017 across all sites was 7% for BOD and 40% for ammonium concentration.