- Title
- Regional scaling of groundwater recharge
- Creator
- Crosbie, Russell Sean
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2003
- Description
- Research Doctorate - Doctor of Philosphy (PhD)
- Description
- This thesis is aimed at providing better groundwater recharge estimates in a shallow coastal aquifer as part of a wider investigation into the sustainable yield of such aquifer systems. Current techniques for measuring recharge provide estimates at various scales, both temporal and spatial. These scales may be different from those required for yield calculations. It is therefore necessary to provide methods that can both aggregate and disaggregate recharge measurements. Yield calculations do not adequately account for uncertainty in recharge estimates. The aggregation and disaggregation techniques provided in this thesis show how to estimate the uncertainty in this parameter and provide indications of the data requirements of the methods. Finally it is shown that yield calculations require accurate determination of mass balance. For aquifers with shallow water tables, this means that it is necessary to determine plant water use and its impact on recharge. This thesis examines each of these questions. Small spatial scale estimates of recharge have been made using two commonly used techniques: the water table fluctuation method and the chloride mass balance method. These estimates of recharge were scaled up from the observational scale to provide two spatially averaged recharge estimates for the whole aquifer. These two methods of recharge estimation are measuring a different quantity of water. The difference between these two methodologies is an estimate of the evapotranspiration from the saturated zone. A time series model has been developed to facilitate the use of the water table fluctuation method of estimating recharge. The model uses a variable specific yield based upon the soil moisture retention curve, filters out the influence of the Lisse effect on the water table and is capable of detecting recharge even if the water table does not rise. It is shown that high temporal resolution water level data and a variable specific yield are essential for the accurate estimation of recharge using the water table fluctuation method. This study has shown that considerable amounts of data are required to utilise the chloride mass balance method for estimating recharge if the uncertainty is to be reduced sufficiently to give an estimate that can be used with confidence. It is shown that a single observation of the chloride concentration of the groundwater can have as much as 50% deviation from the average, leading to 50% errors in recharge estimates. If observations are averaged over 100 days the error reduces to 20% and after 10,000 days the error is expected to be less than 10%. The chloride mass balance results in long term average values of recharge. Which have been disaggregated in time using a water balance methodology. In the aquifer under investigation, the average annual recharge flux is between a half and a third of the available storage. This means that the temporal variability of the recharge is extremely important in the sustainable use of the aquifer if the available storage is not to be depleted. Annual recharge estimates were found to be well correlated with the annual rainfall, but the annual evapotranspiration sourced from the groundwater was found to be inversely related to the annual rainfall. In a drought period there will be reduced recharge and increased discharge by phreatophytes. A simple example has been used to show how these two observations can be incorporated into a probabilistic determination of the sustainable yield of the aquifer.
- Subject
- groundwater; regional; coastal aquifer; recharge; THESIS 2812
- Identifier
- http://hdl.handle.net/1959.13/1486831
- Identifier
- uon:51969
- Rights
- This thesis © 2003 by Russell Sean Crosbie is licensed under CC BY-NC 4.0: https://creativecommons.org/licenses/by-nc/4.0/ Unless otherwise noted, any third-party material reproduced within is © the respective owner and is excluded from this licence.
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 8 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 375 KB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT04 | Supplementary Files | 76 MB | Zip Compressed File | View Details Download |