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Regional Water Accounts and the Transformation of Spatial Data

Regional Water Accounts and the Transformation of Spatial Data. 11 th meeting of the London Group (Johannesburg, 26-30 June 2007). Outline. Introduction Concepts Sources Reallocation methods Accuracy Conclusion. Introduction. Water accounts generally for national level and annual

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Regional Water Accounts and the Transformation of Spatial Data

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  1. Regional Water Accounts and the Transformation of Spatial Data 11th meeting of the London Group (Johannesburg, 26-30 June 2007)

  2. Outline • Introduction • Concepts • Sources • Reallocation methods • Accuracy • Conclusion

  3. Introduction • Water accounts generally for national level and annual • Increasing interest in regional water accounts • River basin is internationally recognized as the unit of reference for IWRM • Physical water data – physical regions + water year vs monetary data – administrative regions + financial year • Objective: Analyze different approaches in transforming data from one space or time boundary to another

  4. Concepts (1) • Spatial Boundaries • Physical (continent, river basin, catchment, aquifer) • Administrative (country, state, municipality, urban water authorities) • Accounting catchment • Temporal Boundaries • Calendar year • Financial year • Water year

  5. Concepts (2) • Administrative: statistical classifications • Physical: no statistical classification system • Distinction foggy • Country borders override river basins • Aquifers vs surface water • Accounting catchment: hybrid areas with best possible matching

  6. Sources Compilation based on data collected for other purposes and by multiple agencies • Scientific measurement • E.g. streamflow gauges, meter use: often precisely located • Surveys • specific area + point in time • Administrative data • license registers, real estate registers etc.

  7. Reallocation methods (1) STEP 1: Assign primary spatial boundary to accounting catchment STEP 2: Reallocate when overlap • Based on correlation with area, population or other variable • Based on correlation and additional data • More precise location of water users • Exclusion of certain areas

  8. Legend River basin boundary Administrative boundary River Region A River Basin 2 River Basin 1 Region A Reallocation methods (2)

  9. Common issues • Data availability • Cross-boundary activities • Confidentiality • Accuracy

  10. Accuracy • Reallocation produces errors • Model specification error (homogeneity?) • Example from Australia

  11. Conclusions • Temporal errors not documented • There is a demand for regional water accounts • Specification of accounting catchments country specific • Existing data have to be reallocated • Accuracy of reallocation has received little attention • When reported, errors were large Recommendations: • Define accounting catchments early in the development of accounts • Design data collection to allow construction of regional water accounts

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