Maria Mimikou

Regional impacts of climate change on water resources quantity and quality indicators

Abstract The aim of this paper is to assess the impacts of climate change on water resources (surface runoff) and on water quality. Two GCM-based climate change scenarios are considered: transient (HadCM2) and equilibrium (UKHI). A conceptual, physically based hydrological model (WBUDG) is applied on a catchment in central Greece, simulating the effect of the two climate scenarios on average monthly runoff. A newly developed in the stream model (R-Qual) is applied in order to simulate water quality downstream of a point source under current and climatically changed conditions. Simulated parameters include monthly concentrations of BOD, DO and NH 4 + . Both scenarios suggest increase of temperature and decrease of precipitation in the study region. Those changes result in a significant decrease of mean monthly runoff for almost all months with a considerable negative impact on summer drought. Moreover, quality simulations under future climatic conditions entail significant water quality impairments because of decreased stream flows.

Regional hydrological effects of climate change

The regional hydrological effects of the expected climate change (i.e. increase of the annual temperature due to the increasing concentration of atmospheric CO2 and other trace gases) and the spatial and temporal redistribution of the regional water resources under various future climatic scenarios are examined by using data of the central mountainous region of Greece, comprising three drainage basins of the Upper Acheloos and the Portaikos Rivers.

Regionalization of flow duration characteristics

The flow duration curve is regionalized by using morphoclimatic characteristics of the drainage basin. The monthly flow duration characteristics at eleven major flow measuring sites across the western and northwestern regions of Greece were first parameterized. Using multiple regression techniques, the geographic variation of each parameter of the best fitted flow duration model is explained in terms of the mean annual areal precipitation, the drainage area, the hypsometric fall and the length of the main river course from the divide of the basin to the site of interest. The regionalized regression equations are successfully used to synthesize flow duration curves at other locations within the hydrologically homogeneous regions of western and northwestern Greece. The method is useful in obtaining estimates of water availability for hydropower at ungaged sites (especially for small hydropower plants, for run-of-river plants), or for other water resources development (water supply, water quality projects), within the regions studied, where the main governmental interest for water resources development is focused.

Description of nine nutrient loss models: capabilities and suitability based on their characteristics

In EUROHARP, an EC Framework V project, which started in 2002 with 21 partners in 17 countries across Europe, a detailed intercomparison of contemporary catchment-scale modelling approaches was undertaken to characterise the relative importance of point and diffuse pollution of nutrients in surface freshwater systems. The study focused on the scientific evaluation of different modelling approaches, which were validated on three core catchments (the Ouse, UK; the Vansjo-Hobøl, Norway; and the Enza, Italy), and the application of each tool to three additional, randomly chosen catchments across Europe. The tools involved differ profoundly in their complexity, level of process representation and data requirements. The tools include simple loading models, statistical, conceptual and empirical model approaches, and physics-based (mechanistic) models. The results of a scientific intercomparison of the characteristics of these different model approaches are described. This includes an analysis of potential strengths and weaknesses of the nutrient models.

Climate change impacts on the reliability of hydroelectric energy production

Abstract This paper presents the assessment of climate change impacts on some critical water management issues such as reservoir storage and hydroelectric production. Two equilibrium scenarios (UK Meteorological Office High Resolution model, UKHI and Canadian Climate Centre model, CCC) referring to years 2020, 2050 and 2100 and one transient scenario (UK High Resolution Transient output, UKTR) referring to years 2032 and 2080 were applied to represent both “greenhouse” warming and induced changes in precipitation and potential evapotranspiration. By using these scenarios, the sensitivity of the risk associated with the annual hydroelectric energy production of a large multipurpose reservoir in northern Greece has been evaluated under conditions of altered runoff. It is shown that the operational characteristics of the reservoir designed and operated under current climatic conditions are, in general, affected by the climate change scenarios examined. Increases of the risks associated with the annual quanti...

Regional climate change impacts: I. Impacts on water resources

Regional effects of greenhouse warming on water resources, and more specifically on surface runoff, are assessed for a mountainous region of central Greece comprising four drainage basins by using a conceptual model and plausible hypothetical scenarios of temperature and precipitation change. Results show considerable sensitivity of runoff characteristics to climate change and indicate certain basin morphoclimatic characteristics such as snow cover, basin aridity and morphology, runoff coefficients etc., which modify considerably basin response. Research work is complemented by assessing the climate change impacts on water management works of the area. This second part of the work is published separately in the following paper in this issue.

An investigation of suspended sediment rating curves in western and northern Greece

ABSTRACT The suspended sediment rating curves for six stations on four rivers in western and northern Greece are investigated. For each station the suspended sediment load is a power function of the water discharge, which may be distinguished according to wet and dry seasons; the latter yields higher sediment loads for a given discharge than the former. This is due to the higher erosivity of dry season rainfall compared to wet season rainfall producing the same runoff. All rating curve exponents b lie in the range 2.5–3.5 for the wet and 2.0–3.0 for the dry season and are related to the constants a of the curves by empirical equations. The variation in a and b is explained in terms of the annual precipitation and area of the basin, the hypsometric fall, the main channel length, and the average bedslope of the river from the basin divide to the station, through empirical relationships, which also permit the prediction of rating curves for ungauged basins.

Human implication of changes in the hydrological regime due to climate change in Northern Greece

Abstract This paper examines the impacts of climate change on various forms of water resources and on some critical water management issues. The study area is the Aliakmon river basin including three subbasins of hydrological interest located in northern Greece. A monthly conceptual water balance model was calibrated for each subbasin separately, using historical hydrometeorological data. This model was applied to estimate runoff values at the outlet of each subbasin under different climate change scenarios. Two equilibrium scenarios (UKHI, CCC) referring to years 2020, 2050 and 2100 and one transient scenario (UKTR) referring to years 2032 and 2080 were implied. It was found that reduction of the mean annual runoff and mean winter runoff values, as well as serious reduction of the summer runoff values would occur in all cases and basins. However, the runoff values for November, December and January were increased, whereas the spring runoff values were decreased, leading to a shifting of the wet period towards December and severe prolongation of the dry period. Moreover, the results indicate that all subbasins exhibit almost the same behavior under the different climate change scenarios, while the equilibrium scenarios (UKHI, CCC) seem to give more reasonable and consistent results than the transient scenario (UKTR). Finally, the negative effects of the climatically induced changes on the hydroelectric production and the water use for agricultural purposes in the study basin were assessed.

Predicting the mean annual flood and flood quantiles for ungauged catchments in Greece

Abstract The spatial variation of the mean annual flood of both mean daily and instantaneous extremes and of the parameters of the Extreme Value Type 1 (EV1) distribution for catchments in the northwest and west regions of Greece are significantly explained in terms of physiographic and climatological characteristics of the catchments by using multiple regression techniques. The catchment characteristics used in the study are the following: drainage area, mean annual areal precipitation, stream frequency, main stream slope and length, intensity of the one-day rainfall of five-year return period, and a soil type index. The EV1 distribution has been found to describe adequately the annual frequency distributions of the daily and of the standardised by-their-mean-value daily extremes of the catchments. Based on the regional models for the parameters of the distribution, annual flood frequency curves, and thus flood quantiles of the assumed distribution, can be derived. The developed regional models are succe...

Flood forecasting in transboundary catchments using the Open Modeling Interface

Using satellite data for flood forecasting in catchments located in mid-latitudes is challenging to engineers and model developers, in no small part due to the plethora of data sets that need to be retrieved, combined, calibrated and used for simulation in real time. The differences between the various satellite rainfall data products and the continuous improvement in their quantity and quality render the development of a single software tool, able to read and process all the different data sets, particularly difficult. Even if such an endeavour was undertaken, the degree of flexibility and extensibility that such a tool would require to accommodate future versions of data sets, available in different file formats as well as different temporal and spatial resolution should not be underestimated. This paper describes the development of a flood forecasting system that addresses this issue through a modular architecture based on the use of the Open Modeling Interface (OpenMI) standard, which facilitates the interaction between a number of separate software components. It is suggested that this approach greatly simplifies programming and debugging and eliminates the need to create spatial and temporal transformation functions without significantly compromising the overall execution speed. The approach and system were tested for forecasting flood events within a particularly challenging transboundary catchment, the Evros catchment, extending between Greece, Bulgaria and Turkey. The system uses two sets of data sources, as an example (NASAs TRMM 3B42 and 3B42RT satellite data sets) to forecast flooding in the Evros catchment. Results indicate that OpenMI greatly facilitates the complex interaction of various software components and considerably increases the flexibility and extensibility of the overall system and hence its operational value and sustainability.