Hydro G Final report - Kildare.ie

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Hydro-G FINAL REPORT 4. Conceptual Model of Leixlip Spa Flow Patterns The observed flow patterns throughout the site were detailed in Section 3.2. Based on the physiochemical monitoring, hydrochemical analyses and flow rate assessments at the Leixlip Spa site, the following model of the hydrological regime is proposed: Water at the Leixlip Spa site originates from a complex groundwater system combining two sources: a deeper, older and warmer groundwater system, discharging at the top of the first terrace through the Spa Well; and a more recent, shallow groundwater that flows through the karstified limestone bedrock with the main groundwater discharge located in the vicinity of the ‘filtering ponds’. Rainfall runoff also plays a part. Hydrochemical analysis suggests that groundwater discharging from the warm spring at the Spa Well is highly mineralised and is the dominant source of water within the site. It is also evident that warm water discharging from the Spa Well drains northwards and flows into and through the shallow system, resulting in water being mixed with more recently recharged water. Groundwater flow in the shallow system also travels through conduits, one of which is evident of the east side of the face of the terrace bounding the 2nd and 3rd terraces. Due to the steep topography of the site, shallow depth of subsoil (if any) and karstic nature of bedrock, groundwater can easily discharge through rock faces and later flow over ground toward the river Rye Water. The main source of water for the site is that from the warm spring known as the Spa Well. This water flows out of the well in northern direction through an underground drain. It is possible that this drain originally ran in a north westerly direction directly to the Roman Bath. However, this design was modified before 1981 and the drain was diverted towards the north east direction towards the two ‘filtering ponds’. It is possible that the original positioning of the underground drain linking the Spa Well and the Roman Bath, in a north western direction, was designed to bypass the cold springs (‘filtering ponds’) to avoid mixing with cooler water discharging from the upper bedrock. However, lack of any evidence of these cold springs on the 6 inch maps, which are usually very accurate for spring discharges, suggests that the cold spring could have resulted from digging out the substrate, which subsequently enhanced seepage and created the fen wetland habitat. Site layout drawings of the 1980’s (Meagher) suggest hat the drying out of the grass wetland on the Intel side of the 1 st terrace may be attributed to repositioning of underground drains and pipes rather than construction of the drain within Intel’s boundary. Further, water quality in the Intel drain shows different hydrochemical signature than samples collected within the Leixlip Spa site suggesting that this water originates from surface runoff. Very little or no water in the drain suggests that this depression does not act as a drainage channel and as such is unlikely to draw water from the grassland reported to be drying out. A cold spring is also located at the ‘filtering ponds’. Based on the disperse distribution of precipitated calcite at the ground surface around the cold spring, it is likely that there are many groundwater discharge points in this area, however the most pronounced is that at the northern end of the Lower Pond. Analysis of flow volumes suggested also that some seepage occurs into the bedrock in the area of the ‘filtering ponds’, reappearing at lower terraces. Seepages and interflows in the subsoil and upper limestone move throughout the site and mix with other groundwater sources, cold springs and rainfall to create a variable habitat controlled by hydrology. Project No.: 07_136 -13- Leixlip Spa
Hydro-G FINAL REPORT There are two distinct water sources at the physical location where the drainage pipe from the Spa Well appears at ground level. Observations and field monitoring data suggest a small, but not significant, leakage from the canal. A number of discrete springs were noted at the 2 nd and 3 rd terraces. Water oozes from the ground and through the cliff face. The physio-chemical analysis suggests that this water is a mixture of the Spa Well water and the shallow system groundwater. Field data suggests that the Spa Well directly influences some conduit flows that are relatively distant from the Spa Well itself. Water flow in the 4 th and 5 th terraces (floodplain) originates mainly from surface runoff contributions from the more elevated upper terraces. No springs were identified within the 4th or 5th terrace. Field data suggest that the Intel boundary drain does not currently act as a drainage channel drawing groundwater from the wet-grassland habitat which has been reported to be drying out. Data from a groundwater monitoring well on the Intel site suggests that water from the deeper groundwater system on the Leixlip Spa site influences hydrochemistry at that location. Project No.: 07_136 -14- Leixlip Spa
Page 1 and 2: HYDROLOGICAL REPORT FOR LEIXLIP SPA
Page 3 and 4: Hydro-G FINAL REPORT PROJECT TEAM D
Page 5 and 6: Hydro-G FINAL REPORT the Intel boun
Page 7 and 8: Hydro-G FINAL REPORT LIST OF FIGURE
Page 9 and 10: Hydro-G FINAL REPORT The issues to
Page 11 and 12: Hydro-G FINAL REPORT 2. Desk Study
Page 13 and 14: Hydro-G FINAL REPORT Hydrochemistry
Page 15 and 16: Hydro-G FINAL REPORT 1983 2008 Phot
Page 17 and 18: Hydro-G FINAL REPORT The general fl
Page 19: Hydro-G FINAL REPORT concentrations
Page 23 and 24: Hydro-G FINAL REPORT suggests that
Page 25 and 26: Hydro-G FINAL REPORT FIGURES Projec
Page 27 and 28: Hydro-G FINAL REPORT 5 km Site Loca
Page 29 and 30: Hydro-G FINAL REPORT Figure 4 Site
Page 31 and 32: Hydro-G FINAL REPORT Appendix A Lei
Page 33 and 34: Hydro-G FINAL REPORT • Deteriorat
Page 35 and 36: Hydro-G FINAL REPORT Temperature, E
Page 37 and 38: Hydro-G FINAL REPORT Iron Iron conc
Page 39 and 40: Hydro-G FINAL REPORT Table 4 Result
Page 41 and 42: Hydro-G FINAL REPORT Project No.: 0
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