Dniester Water Levels Remain Low: Prolonged Decline in Flow May Pose Risks to Odesa’s Water Supply

The hydrological situation in the Dniester basin remains difficult, with no signs of a sustained improvement in water availability so far. According to the latest available data, the water level in the Dniester Reservoir stands at approximately 112.35 metres, while inflow over the past 24 hours fluctuated between only 15 and 29 m³/s. At the same time, downstream discharge remains at 75 m³/s. The level of the Dubăsari Reservoir is virtually unchanged at around 28.06 metres.

On 11 August, the Ukrainian and Moldovan sides, within the framework of the Commission on Sustainable Use and Protection of the Dniester River Basin, agreed to reduce releases from the Dniester Hydropower Complex from 85 to 75 m³/s until the end of August. Ukraine’s State Agency of Water Resources attributed this decision to critically low water availability in the Dniester. According to the agency, on 7 August the lowest inflow into the reservoir since it began operating in 1985 was recorded — 42 m³/s, or only 17% of the norm.

Eco-TIRAS Executive Director Ilya Trombitsky has drawn attention to the ongoing discussion over what level of the Dniester Reservoir should actually be considered critical. According to him, the Moldovan side has requested clarification within the Dniester Commission as to why the Ukrainian side considers a level of around 112 metres to be critical.

At the same time, the officially established dead storage level of the Dniester Reservoir is 102.5 metres, while the normal retaining level is 121 metres.

However, the nearly ten-metre difference between the current level and the dead storage level should not automatically be interpreted as an equivalent “safety margin”. The reservoir has complex hydrological and morphometric characteristics, and its resilience depends not only on the absolute water level, but also on the volume of usable storage, inflow dynamics, required downstream releases, drinking water needs, environmental requirements of the Lower Dniester and expected water availability in the coming weeks.

Institute of Danube Research comment: the Dniester situation directly concerns Odesa

For the Odesa metropolitan area, developments on the Dniester are of particular importance. The Dniester is the main source of centralized drinking water supply for Odesa. Water is abstracted near Biliaivka and then transported to the city through the main water supply system.

For this reason, prolonged low water conditions should no longer be regarded solely as an environmental or transboundary issue. They are also a potential water-security challenge for the Odesa metropolitan area.

There are currently no grounds to claim that Odesa faces an immediate interruption of water supply. However, if the present hydrological trend continues, several interconnected risks may increase.

First, a further decline in river flow could complicate the operation of water intake facilities in the Lower Dniester. A particularly difficult scenario could arise if depletion of the reservoir’s regulating storage causes downstream releases to become increasingly dependent on extremely low natural inflows from the upper basin.

The second factor concerns water quality. Reduced river flow decreases the capacity for natural dilution of pollutants, contributes to higher water temperatures and may weaken the ecosystem’s natural self-purification capacity. Under prolonged low-flow conditions, the water system therefore becomes more vulnerable to pollution.

Another long-term risk for the Lower Dniester is the possible intrusion of more saline water from the Dniester Liman into the river system when extremely low river discharge coincides with adverse wind-driven surges. Scientific studies consider such a scenario particularly important because of its potential implications for the Odesa drinking water intake area. This does not mean that salinisation of the intake is currently occurring, but it represents an additional risk that increases during periods of extreme low water.

Therefore, the seriousness of the present situation cannot be assessed solely by comparing the current level of 112.35 metres with the dead storage level of 102.5 metres. A much more important indicator is the balance between natural inflow, necessary downstream releases and the rate at which accumulated water reserves are being depleted.

According to the Institute of Danube Research, the current situation requires continuous Ukrainian-Moldovan monitoring, transparent exchange of data on actual inflows and reservoir storage, strengthened water-quality monitoring in the Biliaivka intake area, and advance preparation of scenarios for the Odesa metropolitan area in case the Dniester flow declines further.

At present, there is no confirmed information from the Odesa authorities or the water utility operator indicating that restrictions on water supply are being introduced specifically because of the low water level in the Dniester. Therefore, predictions of imminent water rationing would be premature.

Nevertheless, the current hydrological dynamics clearly indicate that Odesa’s water security increasingly requires preventive rather than reactive management.