Climate Change Helmut Kroiss

7/27/2019 Climate Change Helmut Kroiss

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CLIMATE CHANGE AND WATER QUALITY MANAGEMENT

Helmut Kroiss, Institute for Water Quality, Resource and Waste Management

Vienna University of Technology

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Introduction

Background of my presentation is a recent study of a consortium of research institutions

(Meteorology, Hydrology, Water Quality Management) in Austria on the adaptation requirements

for water management to climate change. The goal was to derive the necessary adaptation

requirements for water management for the period until 2050 from existing scientific knowledge

and experience (literature) and existing data. It was also required to classify the requirements into

3 classes based on scientific background (hard, medium hard and weak facts or conclusions).

As Bulgaria has a lot of similar conditions regarding morphology, size land use and population it

has been considered that the results of this study are of interest for Bulgaria, too. This seems to be

especially true for the methodology used but also some results might be applicable to Bulgaria

even there are important differences in precipitation and in the influence of the Black and

Mediterranean Sea. As there is a plan to develop a joint strategy for climate change adaptation in
mailto:[email protected]:[email protected]://iwr.tuwien.ac.at/http://iwr.tuwien.ac.at/mailto:[email protected]://iwr.tuwien.ac.at/


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the Danube region it will be necessary to develop a common methodological approach. This

paper should contribute to enhance the discussion on the interpretation (uncertainty) and

validation of modelling results and how to make optimal use of existing data and maybe how to

improve monitoring in the future. This seems to be important as modelling results are used for

decision making on adaptation measures with important economic and political sometimes also

ecological consequences. As financial resources are always limited it is of great importance to

link risk abatement with uncertainty of results of the scientific methods.

(http://geoinfo.lebensministerium.at/filemanager/download/68173/; policy paper, pdf )

Methodological approach

The following methodological toolbox was used for this study.

global climate models developed by IPCC (grid 200 km) the results of the IPCCmodelapplication until 2050 do not show great differences depending of the different scenarios

regarding climate change abatement success

specific local climate model for Austrian climate (COSMO-CLM, grid 20 km) using the

IPCC model as boundary conditions in order to predict future temperature and

precipitation development in 4 selected regions with different climatic characteristics.

statistical analysis of historic hydrological and climatic data for different length of data

series (30 to 100 years) in order to derive trends for extreme events and seasonal and

yearly means (high flow, low flow, temperature in air surface and ground water)

- using recently developed methods like space for time and delta change in

order to improve the classification of the reliability of the predicted consequences

of climate change

- assessment of the consequences of climate change for water quality in rivers, lakes

and ground water, urban water management

Identificationof consequences of climate change forthe national fresh watersystem and

necessary adaptation requirements for water (quality) management with a clear

classification according to the reliability (uncertainty) of thescientific methods applied.

For this study climate change was defined as an external pressure on water systems

comparable to a change of natural conditions in order to clearly distinguish it from direct

anthropogenic influences on water systems. It was assumed that water management has no

(relevant) influence on climate change and therefore cannot contribute to climate change

abatement and that natural, especially aquatic ecosystems, will adapt to the climate change.

Conclusions for Austria
http://geoinfo.lebensministerium.at/filemanager/download/68173/http://geoinfo.lebensministerium.at/filemanager/download/68173/


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The main conclusions from this study for Austria can be summarized as follows if there is

emphasis on water quality related aspects:

Nature will adapt to climate change as it has done in the past. This can have influence on the

reference status (according to EU WFD) of water bodies as temperature regime has markedinfluence on natural aquatic ecosystems. . Already in the past 30 years mean air temperature

has increased by about 1C. Climatic models predict a further increase of mean temperature by

about 1C until 2050. There are regions where the increase of temperature will be higher (1,5 to

2C). The increase in air temperature will result in an increase of the temperature in waters is in

the range of 0,7 to 0,9 C. This can have an effect on the definition of good status of water

bodies which are actually at the borderline between two bioregions.

The temperature effect on receiving water quality in the past 30 to 40 years cannot be analysed

from the existing data because the change in anthropogenic influence has been much more

pronounced than the climate change.

For groundwater it can be stated that in those areas where oxygen concentrations are already low

actually or have been decreasing during the last decennia will get more sensitive to redox

problems, i.e. anaerobic conditions with iron and manganese mobilization affecting primarily

drinking water quality. Where drinking water is extracted from river water fed ground water the

role of organic pollution in the rivers will become more pronounced. Decreasing ground water

oxygen concentrations are probably the best indicator for management decisions.

The climate models are not able to forecast the probability and size of extreme events (high flow

as well as low flow) with low probability. The variation of precipitation and runoff from year to

year is markedly higher than the effect of the increase of the mean temperature, which isclassified as a hard fact. There is e.g. no proof of a trend towards higher extreme high flows

during the last 150 years for river Danube, where the data base is excellent over very long periods

of time. If only the last 30 years are used for trend analysis, there is a trend towards increasing

probability of high flows.

The shift of precipitation from summer to winter (hard fact according to the model calculations

and trend analysis) together with increasing temperature (less snow precipitation) will lead to

higher mean flows in the alpine region. The periods of the year where the probability of high

flow situations is high will shift accordingly. The effect of climate change on high and low flow

situations will be different for different regions. In the alpine region the probability of low flowduring wintertime will decrease the mean flow will increase in winter and spring time mean flow

in summertime will decrease. In some regions the probability and size of high flows will slightly

increase (medium hard fact).

In the regions with low precipitation and low ground water recharge (eastern and southern part of

Austria) the probability of a decrease of the flow during low flow periods will slightly increase.

This can affect agriculture, where an increased application of irrigation can get into conflict with

other uses and where such a conflict already exists the competition will need more sophisticated


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water management. The forecast results are no hard facts as could be shown using different

scientific methodological approaches. It therefore is necessary to improve monitoring and

modelling tools in these regions to be able to react in time to the consequences. Also in this

respect the changes between the years are much more pronounced than the climatic effects. It is

therefore recommended to use the experience from extremely dry seasons in the past (e.g.

summer 2003, winter 2007) in order to streamline remedial actions.

Urban water systems might also be affected but there the anthropogenic changes are definitely

much more relevant than climate change. The urban water supply and sewer systems have to be

adapted to extreme events with low probability. These cannot be predicted by the climate models.

Adaptation of water supply systems normally has been driven by extreme dry periods in the past

and is therefore most of them are already resilient towards the hard facts derived from the climate

change forecast. The same is for sewer systems where design is normally based on a forecast of

the development in the catchment for the next 50 to 100 years and contains therefore huge

uncertainties mainly caused by unpredictable or uncontrolled anthropogenic influence. There is

no need to include the effect of climate change in to existing guidelines, as they comprise thestatistical trend analysis of extreme events withlow probability during the recent past. If the

probability of flood events in a sewer catchment does not meet the standards the correct response

will be to either reduce the impervious areas or to reduce the effect of flooding on the

infrastructure.

Temperature rise by climate change will affect also lakes. Oligotrophic lakes, where phosphorus

availability is low, will not be affected due to their high resilience. Eutrophication process will be

enhanced by the higher temperature but the effect will be relatively low. As most of the lakes in

Austria are oligotrophic and well protected from phosphorus discharge, this problem will not

cause relevant adaptation requirements.Eutrophication of rivers already today represent a problem for many small rivers especially in

agricultural regions of the northern and eastern part of Austria, where phosphorus is not limiting

algae growth the temperature increase caused by climate change will slightly increase this

problem due to the increase of algae growth rate.

Summary

Summarising it can be stated that adaptation requirements will have to be implemented where the

vulnerability of existing infrastructure is already high today or where the actual resilience of

water bodies regarding water quality is low. This conclusion is supported by the fact that natural

variability of climatic conditions is higher than the reliably predictable consequences of climate

change until 2050. As sound water management continuously has to adapt to extreme events as

high flow events and droughts a well-managed water infrastructure tends to have a high

resilience.

During the past 40 years, where a similar climate change has occurred as predicted by the climate

models for the next 40 years, anthropogenic influence was absolutely dominant at least in regard

to water quality.

Climate Change Helmut Kroiss

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