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| Titel |
Using hydro-economic modeling to investigate trade-offs between ecological and economic water management objectives |
| VerfasserIn |
Niels Riegels, Valerie Sturm, Roar Jensen, Charalampos Doulgeris, Flemming Møller, Peter Bauer-Gottwein |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053732
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| Zusammenfassung |
| This study investigates the use of volumetric water pricing as a tool to achieve
some of the ecological status objectives of the EU Water Framework Directive
(WFD). It also estimates the opportunity costs of meeting these objectives. The
study uses a hydro-economic modeling approach in which water availability is
estimated using a hydrologic model and water demands are based on economic uses of
water.
The WFD requires member states to introduce water pricing policies that provide
incentives for efficient use and contribute to the environmental objectives of the Directive. In
this study, a single volumetric water price is applied to all wholesale water users in a river
basin. The same price is applied to surface water and groundwater. The price does not vary
with time. The single volumetric price approach is compared to a second approach in which
groundwater and surface water are priced differently.
Water users in the basin are assumed to respond to water price changes according to
neo-classical economic theory. Water use is adjusted according to the principles of profit and
utility maximization. Urban/domestic, irrigation, industry, livestock, and tourism water users
are included in the study.
Two approaches for representing farmer responses to water price changes are compared.
The first approach is the residual imputation method, which assumes that willingness
to pay for water can be determined by subtracting all non-water input costs from
revenues, with the difference equal to the value of water. The second approach is based
on Positive Mathematical Programming. This approach assumes that observable
allocations of land, water, and other inputs are the result of profit-maximizing behavior
by farmers and uses this information to parameterize non-linear production and
cost functions. In this second approach, willingness to pay for water is assumed to
equal the marginal value of water in production. The approach based on Positive
Mathematical Programming appears to be more useful because it offers a reasonable way to
model deficit irrigation and changes in cropping patterns resulting from water price
changes.
Water prices are increased until flow patterns in 90% of the reaches in the basin exhibit
good ecological status. Ecological status is measured using metrics that compare distributions
of monthly volumes observed during a 20-year simulation period to distributions of natural
flows that would have occurred during the same 20-year period had anthropogenic water use
not taken place.
An iterative optimization approach is used to identify a water price that meets the
ecological objectives of the WFD. In the optimization, water price is the decision
variable. During each iteration, average annual demands are estimated based on the
water price, assuming profit/utility maximization. These demands are translated
into daily demand patterns, which become boundary conditions for the hydrologic
model of the river basin. The hydrological model runs for a 20-year period using
timeseries inputs estimated using historical data. The 20-year period is intended
to capture a reasonable range of conditions that may be expected in the future.
Simulated river flows are compared to estimates of natural flows in order to assess
ecological status. The optimization continues until a water price has been found that
meets ecological status objectives while minimizing opportunity costs to other users.
When surface water and groundwater are priced separately, both prices are decision
variables.
The economic impacts of increasing the water price are concentrated in the agriculture
sector because the lowest marginal value uses of water occur in this sector. The introduction
of different prices for surface water and groundwater reduces the opportunity cost of
achieving a more natural hydrologic regime by reducing the use of surface water for low
marginal value applications. |
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