You are standing on the banks of Wirra Creek, Willunga. Is the creek flowing? Have you noticed that this creek flows year round. Summer and winter. While most of creeks in Willunga township flow only in winter, Wirra Creek flows because it is spring fed where water emerges from the aquifer further up the hill. In winter flow in this creek is a combination of rain runoff from the hills and from the groundwater spring. In summer the creek flow is reduced but the springs maintain a base flow water supply.
How do springs work? Rain water falls on hills and rocks. Some of the water enters the permiable rocks forming aquifers. Springs occur near the base of hills when groundwater is under artesion pressure or where fractures in rock aquifers intercept the land surface. The spring that feeds this creek surfaces higher up the hill slope and is fed by a fractured rock aquifer. The groundwater from the spring then flows into swamps and wetlands with porous soil that slow the water flow. The springs and wetlands are on private land.
Earthcache tasks. You will need a clear container. A clean empty drink bottle or similar is fine.
-Collect a sample of groundwater from the creek. Take care. You do not want to fall in the creek.
-Is the water clear? Why is it in this condition. This answer will change between summer and winter.
-Let the water stand for at an hour.
-Is the water clear now?
-How could human acitivity change the water flow in the creek?