The Marchfeld region

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Unit 11:

Assessment of Different Water Management Alternatives to Reduce Regional Risks

The Marchfeld Case Study

H.P. Nachtnebel

IWHW-BOKU

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Structure of presentation

• Objectives

• Description of the Case Study

• Methodology

• Application

• Discussion and Conclusion

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Objectives

• A region is exposed to several threats

• An approach has to be developed to identify sound solutions

(4)

The Marchfeld region

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Historic map

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The Marchfeld region

• About 1000 km2

• About 60 000 inhabitants

• Intensive agriculture (sugar beets, vegetables, maize,….)

• Low mean annual precipitation (500- 650 mm/a)

• Major wetlands along the Danube and March river

(7)

Major threats in the region

• Overexploitation of groundwater resources

(8)

Groundwater abstraction

(9)

Trend of groundwater table

(10)

Major threats in the region

• Pollution of groundwater resources

(11)

Groundwater pollution

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Nitrate concentration in different agricultural regions

(12)

Major threats in the region

• Pollution of surface waters

(waste water is released to small creeks)

(13)

Surface water quality

• Surface water bodies exhibited (<1985) low discharge and high organic loads

Sugar factories and food processing

(14)

Major threats in the region

• Some areas are exposed to wind erosion

(15)

Wind erosion

• Wind erosion was (is) a severe threat

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Major threats in the region

• Along the major rivers (boundaries) large wetlands of high ecological value are endangered due to

lowering of groundwater

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Major threats in the region

• Along the major rivers (boundaries) large wetlands of high ecological value are endangered

City area Vienna

Flood plain forests and wetlands

Areas endangered by wind erosion

Planned irrigation channel network

(18)

Management objectives

• Identify water resources management

alternatives which reduce the regional risks originating from identified threats

– Support national objectives (agri prod.,..)

– Ensure water supply (domestic, agriculture, industries)

– Support regional interests (avoid regional losses) – Preserve environmental quality

• Assess and rank alternatives

(19)

Management objectives

• Improve national economy

support national self supply with agricultural production equity in regional agricultural incomes

• Improve regional economy

utilise regional resources support regional agriculture preserve jobs in agriculture

• Improve environmental quality

improve surface water quality improve groundwater quality

stabilize the groundwater system reduce wind erosion

preserve wetland areas along the rivers

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Objectives, criteria and measurable units

The general objectives require further specification by subgoals, criteria and measurable units

Criteria can be expressed by cardinal (measurable quantities) or ordinal units (qualitative description)

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Objectives, criteria and measurable units

The general objectives require further specification by subgoals, criteria and measurable units

Criteria can be expressed by cardinal or ordinal units

(22)

Handling uncertainty

• Two indicators describe uncertainty

• Robustness (to internal changes) and

• Independency (of external projects)

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Additional information

• Several other projects are in discussion along the Danube as well as the extension of water intake

schemes in the Southern part of the flood plain forest (Auwald). These projects might have some influence on the groundwater regime and therefore the indicator

„Independency“ has been introduced.

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Actions and alternatives

• Action A1: provide water from Danube via a gravity channel to the region The lower terrace can be supplied by a gravity channel

The higher terrace needs pumping stations (15 m)

implementation level (0, lower terrace, full irrigation)

• Action 2: Efficient water use

Industrial recirculation of process water

(a reduction from 12,2*10⁶ m³/a (now) to 6-7 * 10⁶ m³/a) Improved waste water treatment (industries, domestic wwt- plants

implementation level (0, full treatment)

• Action 3: Increase wind breakers

reduce wind erosion, reduce evaporative losses, improve micro- climate

implementation level (0,1)

• Action 4: Land use:

changing from water demanding crops to oils seeds, sunflower etc.

împlementation level (0,1)

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The alternatives (options)

• The implementation of these alternatives is considered to be independent of each other

• Alternatives could be developed which are between 0 and full implementation. Here we consider only 0, 1.

• Thus, we have overall 3*2*2*2 = 24 alternatives

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Models

• Models are needed to relate actions (alternatives) with outcomes (impacts)

• Groundwater model

• Pollution load (surface and groundwater)

• Wind erosion

• Production model linking water consumption with output

(27)

Possible actions (decisions)

Set of actions

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Systems approach (decisions)

Set of actions Dynamic state space model

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Methodology

• A 2-D unsteady groundwater model was calibrated

• Groundwater recharge was estimated

• Interaction with boundaring rivers was analysed and modeled

• An agro-economic model was applied

• A model for surface water bodies was applied

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Groundwater model

• Identification of boundary conditions

• Identification of initial conditions

• Parameter estimation

• The output refers to the spatial distribution and temporal variation of the groundwater table,

dependent on the taken actions

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Groundwater model (parameters)

Hydraulic conductivity storage coefficients

Groundwater recharge

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Groundwater model

Boundary conditions bottom layer

Groundwater abstraction (industries, domestic) groundwater abstraction (agriculture)

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Mean annual water balance

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Some results

Iso-lines of groundwater table specific flows

Iso-lines of groundwater table spatial pattern of gw flows

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Qualitative evaluation

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Assessment of alternatives

• Each alternative has to be assessed with respect to the various criteria

• Asessing the impacts (Impact table)

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Impact table

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Comparing alternatives

• Electre I was applied

• It uses weights (importance of a criterion) and scales (to measure the difference between two outcomes)

• It is based on a pairwise comparison of alternatives

• The dominance of alternative A_i over A_j is calculated and expressed by the Concordance index C(i,j)

• The weakness of A_i with respect to A_j is calculated by the Discordance Index D(i,j)

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ELECTRE: concordance and discordance

• Concordance expresses the dominance of Ai>Aj

• Discordance expresses the weakness of Ai<Aj

• Thresholds are chosen for C* and D*

• We are looking for alternatives having a high C and a low D

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(40)

Example

Alternative Weigth Scale

A3 A5

Criteria 1 Net Benefit 4 3 2 5

Criteria 2 Water Quality poor good 1 4

Criteria 3 Energy output 5 2.5 2 5

CI(3,5)=4/5 DI(3,5)=2/4

Range very good-good-acceptable-poor-very poor

1 2 3 4 5

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Comparing alternatives

• A preferred alternative should have a high concordance and low discordance

• Alternatives 10, 12, 14, 16 perform well

• What do they have in common ?

- Irrigation of lower terrace (Q₂) and modified land use (L₂) - Implementation of WWTs (G₂) is included in 14 and 16 - 14 and 16 exhibit also much better surface water quality

index

- a full ranking would yield 14>16>10 and 12 - The status quo ranks low

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Comparing alternatives (Impact table)

• A preferred alternative should have a high concordance and low discordance

• Alternatives 10,12,14, 16 perform well

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The technical solution

• Implementation of an irrigation channel diverting water from the Danube to the area

• Only supply of the lower terrace

• Improvement of industrial water use efficiency

• Implementation of waste water treatment plants

• Implementation of wind breakers in most of the region

• Development of a regional drinking water supply scheme utilising gw in the flood plain

(44)

The technical solution

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Discussion and Conclusion

• The preferred alternatives have several common features

irrigation of the lower terrace, improved WWT

(46)

Discussion and Conclusion

(47)

Afforestation and implementation of wind

breakers

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Discussion and Conclusion

• Finally the implementation was executed in the same way (until now)

• Additionally wind breaker facilities were extended

(49)

Discussion and Conclusion

• Additionally wind breaker facilities were extended

(50)

Discussion and conclusion

irrigation of the lower terrace improved WWT

• Additional wind breaker facilities were implemented

• In the last years a modification in the cropping pattern has been observed

(51)

Discussion and conclusion

• A company was established to manage the

water distribution from the channel to the fields

• The company wanted to sell the water to cover its operation costs

• Farmers refused to pay and preferred to continue with groundwater pumping

• Finally it was politically decided to recharge the groundwater system and to distribute the water via the gw-system

(52)

Discussion and conclusion

• The project has reduced regional risks (water availability, agricultural production,

environmental degradation)

• The project was definitely in the interest of regional economy

• It did not fully support objectives of the national economy

• Public participation (although not legally requested) worked well

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Location of the recharge sites

Recharge Sites

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Summary and conclusion

• Besides augmentation of the GW level the channel also serves ecological purposes

• Until today only a small amount of water is taken directly from the channel

• Farmers continued to pump from groundwater instead of paying for water

• Two groundwater recharge facilities were built to supply the farms via the groundwater system

• Plans are discussed to apply a similar approach