Hydrological characteristics of Chernobyl catchment: assessment of
catchment scale long-term water balance and future situation
Abstract
Changes in the catchment scale water balance have important social
implications for usable water now and in the future. Stream discharge is
also directly related to radionuclides flux in the river water system.
The aim of this study was to clarify the water balance in the Chernobyl
Exclusion Zone (CEZ) under current and future climate conditions. A
catchment scale hydrological model was used with long-term discharge
data to project the future trend of radionuclides wash-off from the
contaminated catchment at the CEZ in Ukraine. The Sakhan river catchment
at the CEZ (51.41°N, 30.00°E) in Ukraine is one of the Pripyat river
systems, and has a total surface area of 186.9 km2. We
found that under the current climate, 84% of annual input (sum of
rainfall and snowmelt) was consumed as evapotranspiration, and discharge
was estimated to be 16%. In future climates, annual precipitation is
expected to increase. However, a projected increase in the vapor
pressure deficit led the consumption of precipitation as
evapotranspiration and no significant increase in discharge. The study
found that warmer winter and spring temperatures will decrease the
snowfall, and increase the rainfall, but it was not enough to increase
evapotranspiration. As a result, the peak of discharge shifted from
April to March. The increase of future average discharge during the
winter and spring came from a combination of (1) increasing rainfall in
the winter and spring, and (2) relatively small levels of
evapotranspiration, which enhanced the catchment scale water recharge in
soil moisture and gave rise to greater discharge during winter and
spring. The reduction of extreme river discharge from the hydrological
projections could reduce the probability of high radionuclides
concentration in the river water system in the future, owing to the
reduction of surface runoff water from the contaminated surface soil
and/or top layer of floodplain soils in the CEZ.