water balance estimation 1 naomi radke, seecon international gmbh

Water Balance Estimation


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Naomi Radke, seecon international GmbH


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Contents

1. What is a Water Balance Estimation

2. Who is Involved?

3. What Can it be Used for?

4. Uncertainty and Problems

5. Conducting a Water Balance Estimation

6. Applicability

7. Advantages and Disadvantages

8. References

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A water balance estimation is ...

... A tool to assess the current status and trends in water resources availability in an area over a specific period of time.

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1. What is a Water Balance Estimation?

Change in global water availability. A

water balance estimate can reveal

the situation of water availability.

Source: UNEP GRID-A (2009)



Calculating the water balance

The simplest form of water balance estimation is:

P = Q + E ± ∆S

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P: PrecipitationQ: RunoffE: Evaporation∆S:Storage in the

soil, aquifers or reservoirs

Example of water balance estimation. Source:

BGR (2008)



Conservation of water ...

... If in a specific area over a specific time

water inflows = water outflows ± changes in storage

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Precipitation (rainwater) is either transferred to surface run off or evaporates OR it is stored in the ground.



• Stakeholders involved in decision-making that require more detailed info on water available

• Specialists or staff that have undergone training and access to specialist support

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2. Who is Involved?

RiverWare (a river system modelling tool)Training in Mexico.

Source: Water Balance Consulting (2013).



• Asses the current status and trends in water resource availability in an area over a specific period of time

• Strengthen water management decision-making by assessing and improving the validity of visions, scenarios and strategies

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3. What Can it be Used for?

Managing aquifer recharge/discharge. Source: FAO et al. (2012)



Uncertainty in water balance estimation

There is always uncertainty due to inadequate capture networks, measurement errors, complex spatial and temporal heterogeneity of hydrological processes

Uncertainty Analysis is an important part of water balance estimation!

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Problems occurring in water balance estimation

• Temporal and spatial boundaries are not defined

• Quality of input data is poor

• Double counting of water flows when water flows within an area added to water flow of exiting area

• Inappropriate extrapolation of field level information to a larger scale

• Intuition (often based on popular myths) is used rather than good quality information.

• The storage term(s) of the water balance is omitted

• Political or other pressures result in unreliable estimates that have been manipulated

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Materials and Resources

• Techniques: From very simple “back of the envelope” calculations to highly complex computer-based models

• Precondition: Sound knowledge of hydrological processes

• Advisable o To contract specialist serviceo To have access to a quality-controlled information

database

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Methods (1/2)

• Step1: Define boundaries of the area of interest

• Step 2: Undertake a needs assessment of the water balance information that is required among stakeholders. Define water balance components of particular interest

• Step 3: Produce a simply schematic diagram that shows storage, inflows and outflows from the area of interest

• Step 4: Identify a source(s) of quality-controlled info, relevant for area and period

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Methods (2/2)

• Step 5: Uncertainty and sensitivity analysis on this info. If inadequacies, redefine the boundaries and/or modify equation

• Step 6: Produce water balance estimates in a format that is useful for visioning, scenario building and planning with the community

• Step 7: Control these estimates regarding their quality before they are disseminated

• Step 8: Disseminate findings to stakeholders in a form they can understand

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Result Example

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Australian water balance report. Source: NWC (2005)



Water balance estimation as basis for ...

• Quantitative evaluation of water resources and their change under human activities

• Hydrological substantiation of projects for the rational use, control and redistribution of water resources in time and space

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6. Applicability

How does irrigation effect the water availability? A water balance

estimation can help assess the severity of human impact on the

water cycle. Source: B. Haas



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7. Advantages and Disadvantages

Advantages:•Provides you with a

comprehensive understanding of the water flow system and water resources in your area

Disadvantages:•Often incorrect for the

many reasons listed before•Often, minimal or no

account is taken of uncertainty when estimates are made and presented

•Very complex work process that needs to be done by qualified experts (at least as support) which requires considerable time and resources



BGR (2008): Water Cycle/Water Balance for Germany. Hannover: Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR). URL: http://www.bgr.bund.de/EN/Themen/Wasser/Bilder/Was_wasser_startseite_wasserkreis_g_en.html [Accessed: 14.10.2013]

Water Balance Consulting (2013): RiverWare Simulation Training in Mexico. Boulder: Water Balance Consulting. URL: http://waterbalance.org/projects-page/riverwaretraining/ [Accessed: 14.10.2013]

FAO, GEF, IAH, IHP, World Bank (2012): Management of aquifer recharge and discharge processes and aquifer storage equilibrium. Rome: FAO. URL: http://www.zaragoza.es/ciudad/medioambiente/onu/en/detallePer_Onu?id=587 [Accessed: 14.10.2013]

NWC (Editor) (2005): Australian Water Resources 2005 - Water Balance Assessment. Canberra: Australian Government, National Water Commission (NWC). URL: http://www.water.gov.au/WaterAvailability/Waterbalanceassessments/index.aspx?Menu=Level1_3_2 [Accessed: 14.10.2013]

UNEP GRID-A (2009): The Contribution of Climate Change to Declining Water Availability. Arendal: United Nations Environment Programme (UNEP) GRID Arendal. URL: http://maps.grida.no/go/graphic/the-contribution-of-climate-change-to-declining-water-availability [Accessed: 14.10.2013]

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8. References

Water Balance Estimation 18

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