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Physical hydrogeology 45

BO X
Continued
2.6

through the Qu’Appelle Valley at Katepwa Provincial Park (Fig. 1) form of major springs. It is conjectured that discharging groundwa-
shows recharge from rainfall and snowmelt on the adjacent prairie ter carried sand and gravel from the Echo Lake Gravel and, to a
moving vertically downwards to the Echo Lake Gravel and Empress lesser extent, from the Empress Group into the Qu’Appelle Valley,
Group, then horizontally through these more permeable deposits, where part of it was swept away by meltwater flowing through the
before finally moving vertically upwards to discharge into Katepwa Qu’Appelle Spillway. This loss of sand and gravel by ‘spring sapping’
Lake as underwater springs. caused the overlying till to collapse, forming a tributary valley,
The evolution of the tributary valleys, as shown in Fig. 2, is linked which developed headwards along the path of maximum ground-
to past and present groundwater flow regimes. At the time the water flow. Spring sapping forms short, wide tributaries and
Qu’Appelle Valley was cut by glacial meltwater, the water-bearing accounts for the short, well-developed gullies observed in the valley
Echo Lake Gravel was penetrated, and large quantities of ground- sides that deliver material to build the alluvial fans that today pro-
water discharged from this aquifer into the Qu’Appelle Valley in the ject into Katepwa Lake.

Fig. 2 Block diagram showing the final
stage of evolution of tributary valleys and
alluvial fans by spring sapping in the
Qu’Appelle Valley, Saskatchewan. After
Christiansen et al. (1981).

common type and result from the location of a springs may form at times of higher water table eleva-
major barrier in the path of the underground drain- tion. Confined springs arise where artesian conditions
age. The barrier may be caused by another lithology, are caused by an overlying impervious formation.
either faulted or in conformable contact, or be caused Fault planes occasionally provide a discharge route
by valley aggradation, such as by the deposition of for the confined groundwater as in the case of the
glacial deposits. The denser salt water of the sea also Bath thermal springs (Box 2.7) and the example of
forms a barrier to submarine groundwater discharge the Permian Magnesian Limestones in South York-
of freshwater. In each case, temporary overflow shire (Fig. 2.20). Elsewhere, the groundwater escapes