University of Twente Student Theses
The effect of leaky weirs on groundwater tables in the Mulloon catchment
Meinen, J.G. (2022) The effect of leaky weirs on groundwater tables in the Mulloon catchment.
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| Abstract: | This thesis is about the leaky weir structures installed in Mulloon creek and their effect on the groundwater in Mulloon catchment. 38 piezometers, 2 rain gauges, and a stream gauge installed in the catchment have been gathering data over varying periods between December 2015 and September 2022. This report describes the process of a Pearson correlation analysis, a time series cross-correlation analysis, and a quantitative analysis of the change in water height in the piezometers relative to either rainfall in millimeters over a day or to the number of days without rainfall. The correlation analysis found 207 pairs of piezometers correlated .85 or above. This list was shortened to a group of 44 pairs of piezometers based on whether the water height in a piezometer in a pair was correlated .85 or above with the water height in the stream. This list of 44 piezometer pairs was then used in the cross-correlation analysis. The result of this analysis were lag times between piezometers. The list of 44 piezometers was then also used in the quantitative analysis. The correlation analysis showed that there probably is some form of flow between groundwater aquifers in the catchment. The cross-correlation analysis showed that there probably is no flow between transect 2 and transect 4, but there might be a flow between transect 3 and transect 4. Tracer tests could give conclusive evidence on this subject. When looking at all available data, the quantitative analysis showed that the recharge rate of most piezometers and the discharge rate of some piezometers increased after the leaky weirs were installed. When only looking at the data from the dry period, the increase in the recharge rate was not present anymore, but the increase in the discharge rate was still observed. This suggests that the weather that the catchment experiences has a large influence on these rates. In the future, the analysis should be repeated for post-leaky weir periods that are similar in weather to the pre-leaky weir periods. The conclusion of this research is that there is likely flow between several groundwater aquifers in the catchment, but which aquifers those may be is yet undefined and the effect of the leaky weirs on these flows thus remains unknown. Also, the leaky weirs may have an effect on the recharge and discharge rates of the piezometers, however for conclusive evidence the analysis has to be repeated on a dataset with limited variability in rainfall. |
| Item Type: | Essay (Bachelor) |
| Faculty: | ET: Engineering Technology |
| Programme: | Civil Engineering BSc (56952) |
| Link to this item: | https://purl.utwente.nl/essays/93674 |
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