Regional impacts of climate change on water resources quantity and quality indicators
Introduction
The research work presented herein originates from two EU funded research programmes (EUROTAS and CHESS, both funded under the fourth FP—DGXII) that address the impacts of ‘greenhouse’ warming on water resources quantity and quality on a catchment, regional and European scale.
The study area is the Pinios river basin, situated in the central part of Greece. Because of an intensive cultivation, water needs are considerable. Additionally, the large application of pesticides and fertilisers can cause serious degradation of the quality of the surface and groundwater of the basin. Because of physical, chemical and biological processes occurring within the river, the river's role is far from that of a conduit for the transport of inputs. These processes have a strong purifying effect leading to an improvement of water quality downstream from a source of pollution. A quality parameter of primary importance that accelerates these processes is the dissolved oxygen concentration. Hence purification is largely dependent on the continued oxygenation of the river water, which is enhanced under high flow conditions that encourage surface aeration. On the contrary the aggregated contribution of pollutants under low flow conditions can cause serious downstream problems regarding water quality. Eutrophication, which is caused by excessive levels of nutrients, is the most notable example.
The climate change scenarios are constructed by the Climatic Research Unit (CRU) of the University of East Anglia (UK) and are the results of two climate change experiments based on the General Circulation Models (GCM) (Hulme et al., 1994). More specifically, one equilibrium experiment, UKHI and one transient experiment, HADCM2 are applied. Changes refer to rainfall, temperature and potential evapotranspiration.
In order to estimate the hydrological effects of climate changes, a conceptual, physically based water balance model (WBUDG), developed for this purpose, is applied. It allows the calculation of surface runoff, soil moisture and actual evapotranspiration. Water quality parameters are estimated by using an in stream model (R-Qual), which in combination with the WBUDG model allows a complete simulation of flows and water quality, under current and changed climatic conditions up to the terminal year 2050.
Section snippets
Study region and data used
The Pinios river is located in the Thessaly district (central part of Greece) The total drainage area of the river is 9.450 km2, with a varied topography from narrow gorges to wide flood plains.
The Pinios catchment area consists of 15 sub basins drained by the main river and its five most important tributaries. Owing to lack of sufficient data for most sub basins, the study focuses on the Ali Efenti sub basin (Fig. 1), for which reliable hydrometeorological time series of adequate length are
Climate change scenarios
The climate scenarios used have been constructed by the Climatic Research Unit (CRU) of the University of East Anglia, England.
The methodology adopted used the CRU 1961–1990 baseline climatologies for Europe, the results from two GCM (General Circulation Models) climate change experiments (UKHI and HadCM2) and a range of projections of global warming calculated by MAGICC (Model for the Assessment of Greenhouse gas Induced Climate Change), a simple upwelling-diffusion energy balance climate
Water quantity
The assessment of climate change impacts on several water resources quantity indicators was based on the use of a monthly water balance model (WBUDG), developed for this purpose. The flow chart of the model structure is shown in Fig. 2. The main input parameters are precipitation, temperature, relative humidity, sunshine duration and wind speed. The main output parameters are evapotranspiration, soil moisture and stream runoff. Details on the model operation can be found in a series of previous
Results
Table 6 presents the mean monthly runoff for the terminal year 2050, regarding the base run, UKHI change and HadCM2 change. Additionally and for comparison, the percent increase or decrease of the climatically changed runoff from the base run is also given.
It has been estimated that there will be a significant decrease of the mean monthly runoff for all months by taking into account climate change from the transient experiment. A significant decrease of the mean monthly runoff for almost all
Conclusions
Basic conclusions drawn from this research are the following:
- •
Both scenarios seem to give reasonable and quite consistent results. The transient scenarios (HadCM2) give more significant changes than the equilibrium (UKHI).
- •
Mean annual runoff values are reduced.
- •
Mean winter runoff values (November–April) are reduced.
- •
The most significant reduction is expected in mean summer runoff values (May–October).
- •
The results on runoff change are in accordance with results drawn from previous relevant research
Acknowledgements
This research was supported by the Environment and Climate Programme of the EU, DGXII, in the framework of the contracts ENV4-CT97-0535 (EUROTAS: European River Flood Occurrence and Total Risk Assessment) and ENV4-CT97-0440 (CHESS: Climate, Hydrochemistry and Economics of Surface—Water Systems).
References (14)
- et al.
Evaluation of pollution reduction scenarios in a river basin: application of long term quality simulations
Water Science Technology
(1997) - et al.
Modelling in-stream water quality in LOIS
Science and Total Environment
(1998) - et al.
Regional hydrological effects of climate change
Journal of Hydrology
(1991) - et al.
Human implication of changes in the hydrological regime due to climate change in Northern Greece
Global Environmental Change
(1999) The effect of climate change on hydrological regimes in Europe: a continental perspective
Global Environmental Change
(1998)- et al.
A dynamic model for DO-BOD relationships in a non-tidal stream
Water Resources and Research
(1976) Surface Water-Quality Modelling
(1997)
Cited by (164)
The impact of climate change on the water quality of Baiyangdian Lake (China) in the past 30 years (1991–2020)
2023, Science of the Total EnvironmentQuantification of land use/land cover impacts on stream water quality across Taiwan
2021, Journal of Cleaner ProductionModelling and forecasting roots & tubers losses and resulting water losses in sub-Saharan Africa considering climate variables
2020, Physics and Chemistry of the Earth