Citations
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Series / Report no.
Open Access
Type
Report
Language
en
Date
1995-05-31
Research Projects
Organizational Units
Journal Issue
Title
GW_VOL ; The EXPECT Groundwater Level
Module
Translated Title
GW_VOL ; De EXPECT grondwaterstanden
module
Published in
Abstract
Als onderdeel van het integrale milieu-model EXPECT is
een module ontwikkeld voor berekeningen van veranderingen in grondwaterstand
en kwel, die het gevolg zijn van wijzigingen in grondwateronttrekking. Deze
module is opgebouwd uit lineaire ingreep-effect relaties tussen het
onttrekkingsdebiet van een pompput en de effecten op de grondwaterstand en
kwelflux. De relaties zijn afgeleid uit berekeningsresultaten van het
Landelijk Grondwater Model (LGM). De ingreep-effect relaties zijn afgeleid
voor alle 1*1 km gridcellen waarop een onttrekking van invloed is. Effecten
van verschillende onttrekkingen op een gridcel worden gesommeerd. Omdat in
het LGM de relatie tussen stijghoogte in de bovenste aquifer en flux naar
het oppervlakte water niet-lineair gemodelleerd is, zullen lineaire
ingreep-effect relaties slechts een benadering zijn van de resultaten van
LGM. Om een indruk te krijgen van de nauwkeurigheid van de voorspellingen
op grond van de lineaire regressiefuncties is per gridcell de ratio berekend
tussen de door het model verklaarde variantie en de totale variantie. Om
een indruk te krijgen van de verschillen in uitkomst tussen de
grondwatermodule en LGM zijn verscheidene onttrekkings-scenario's zowel met
LGM als met de EXPECT-grondwatermodule doorgerekend en zijn de resultaten
vergeleken.De conclusie is dat zolang geen onttrekkings-scenarios worden
gekozen met onttrekkingsdebieten groter dan de scenarios gepresenteerd in
hoofdstuk 4, de grondwatermodule een goede benadering van LGM resultaten
levert.
As part of the integrated environmental model EXPECT, a groundwater module has been developed which calculates changes in groundwater level and seepage due to changes in groundwater abstraction. The groundwater module uses linear source-receptor relationships between groundwater abstraction rate of a well and changes in hydraulic head and seepage in grid blocks. The relationships are based on calculations with the RIVM groundwater model for the Netherlands (LGM). Source-receptor relationships are derived for all combinations of 1*1 km grid cells and abstraction wells. Effects of different abstraction wells on one grid cell are summed. Because of the non-linear relationship between hydraulic head in the upper aquifer and flux to the surface water system used in LGM, the source-receptor relationships are only an approximation of the LGM results. The ratio between the variance explained by the model and the total variance has been calculated for each grid cell as an indication of the accuracy of the results calculated with source-receptor relationships. Effects of several groundwater abstraction scenarios have been calculated with both the groundwater module and LGM, to get an impression of the differences in results.The conclusion is that, if groundwater abstraction scenarios do not include changes in abstraction rates larger than in the scenarios discussed in chapter 4, GW_VOL can be used successfully to calculate changes in groundwater level and seepage.
As part of the integrated environmental model EXPECT, a groundwater module has been developed which calculates changes in groundwater level and seepage due to changes in groundwater abstraction. The groundwater module uses linear source-receptor relationships between groundwater abstraction rate of a well and changes in hydraulic head and seepage in grid blocks. The relationships are based on calculations with the RIVM groundwater model for the Netherlands (LGM). Source-receptor relationships are derived for all combinations of 1*1 km grid cells and abstraction wells. Effects of different abstraction wells on one grid cell are summed. Because of the non-linear relationship between hydraulic head in the upper aquifer and flux to the surface water system used in LGM, the source-receptor relationships are only an approximation of the LGM results. The ratio between the variance explained by the model and the total variance has been calculated for each grid cell as an indication of the accuracy of the results calculated with source-receptor relationships. Effects of several groundwater abstraction scenarios have been calculated with both the groundwater module and LGM, to get an impression of the differences in results.The conclusion is that, if groundwater abstraction scenarios do not include changes in abstraction rates larger than in the scenarios discussed in chapter 4, GW_VOL can be used successfully to calculate changes in groundwater level and seepage.
Description
Publisher
Sponsors
RIVM
(DGM/SP)