Hydro G Final report - Kildare.ie

Hydro-G FINAL REPORT
Temperature, Electric Conductivity and Total Dissolved Solids
It is evident that water temperatures decrease from the south to north direction, as does the electric
conductivity. The highest temperatures and ECs were recorded in the Spa Well (monitoring point 9,
T=13.5-15°C, EC = 1900-2000 µS/cm) and in the outflow from the underground drain (monitoring
point 8). In the small ‘irony spring’ (monitoring point 7) both water temperature and EC were
recorded at much lower levels (T = 8-10 °C, EC=~750 µS/cm), which were comparable with the
Royal Canal conditions (monitoring point 10; T=5.9°C and EC= 617µS/cm; 10/12/2007) and as such
suggest leakage from the canal. In the next, further down gradient, location in vicinity of the
‘filtering ponds’ temperatures and ECs varied spatially across relatively small distances and were
highest in central points in both ponds and lower at more outer locations. It was also noted that
both the temperature and EC were higher in the Upper Pond than in the Lower and that EC measured
in the Lower Pond on the second occasion were significantly lower than the first time in December.
The depth of water in these ponds was investigated to reveal that both ponds are relatively shallow
with 0.45m depth in the Upper Pond and 0.25m in the Lower Pond. Field investigations suggest that
these ponds are underlain directly with bedrock. Lower temperature and EC in localised places
suggest multiple sources of water at these locations, i.e cold springs which mix with warmer water
coming from the Spa Well. These cold springs are likely to originate in the shallow system which is
expected to be cooler and less mineralised in comparison to water discharging from the deeper
system at the Spa Well. Abundance of calcite precipitated in this area and specifically around the
Lower Pond (monitoring point 18) suggests that groundwater discharges at this location. Integration
of field data suggests that while the Upper Pond is fed by the Spa Well, the Lower Pond also has
inputs from the shallow groundwater system. Monitoring results down gradient of the ‘filtering
ponds’ show temperatures at approximate level of 8-9 °C and EC at around 1750-1850 µS/cm (lower
than in the Spa Well by ~5 °C and ~200 µS/cm).
Water flow on the second terrace is by flow along the ground surface. This prevented monitoring of
physio-chemical parameters. There is an abundance of ad hoc streams wherever topography allows.
Large depositions of calcite were noted where water drops from the first terrace into the second
terrace. Increased flow velocities and more dispersed nature of flow increases the release of the
CO2 from the water, which facilitates higher calcite precipitation rates in this location.
At the third terrace, there was an abundance of water flow and sources. It is likely that not all
discharge points were identified. Water was noted to enter from both overland flow and also from
various sources directly in the ground and bedrock face. Discharge from the bedrock face at the
eastern side of the terrace (monitoring point 3) had relatively low temperatures (7-8 °C) and high EC
values at ~ 1600µS/cm. Some deposition of iron was also noted in the opening in the bedrock,
suggesting high iron content in water. Two other small outflows from the base of the bedrock were
also noted; one in a shallow pool of water where distinct pieces of tufa are present (‘tufa pond’,
monitoring point 22) and the second 1m above this pool (too shallow to measure physio-chemistry).
Physio-chemical characteristics of the ‘tufa pond’ were: T at 6.3 - 8.3°C and EC at ~1480 µS/cm.
There were two sampling points on the fourth terrace; one on the west side (monitoring point 1) and
one at the east side (monitoring point 2). On the east side, water forms a stream of 0.15m width and
0.05m depth and the flow is relatively fast. Deposits of tufa are present in the bed of the stream.
Measured temperatures were 5.5 - 6.8°C on the west side and 6.6 - 6.9°C on the east side. Electric
conductivity averaged 1550 µS/cm.
The drain on the Intel site at the western boundary of the Leixlip Spa site contains water at its
northern end only, which finishes at the approximate elevation of the Roman Bath. Water in this
Project No.: 07_136 -28-
Leixlip Spa