Yes, Your Mighty Waikato EarthCache
Hidden : 6/21/2015
Difficulty:
2 out of 5
Terrain:
1 out of 5

Size: Size: other (other)

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Geocache Description:

The Waikato River has significant influence on Hamilton City. It is the longest river in NZ at 425km starting at Mt Ruapehu through to Port Waikato. Check the geological profile image to see the make up of the river basin.

The ancestral Waikato River flowed from an ancient lake (Lake Huka) in the centre of the North Island through deep gorges of welded ignimbrite and rhyolite,northward through the Hinuera Valley and Hauraki Basin into the Thames Estuary. It is possible that the river flowed through the Waikato Basin about a million years ago before returning to its Hinuera course.

After the huge Oruanui eruption 27,000 years ago pumice was showered all over the North Island to a depth of 200m thick. A new lake was formed - Lake Taupo. The water built up until a new outlet was forced 120m above the present level near Waihora Bay.

Over the next few thousand years the bed of the river was raised by large amounts of eruption debris. Then the original blocked entry suddenly gave way-the lake level fell 75m as about 80 cubic kilometres of water and debris poured out in a catastrophic breakthrough flood causing the river to change course near Pairere. The water level dropped quickly and the river stayed in this new course through the Maungatautari gorge and Hamilton Basin. The mean discharge of the Waikato River is 340 m3 /s, with the highest flows typically occurring in July and August. Specific mean annual floods are low (60-70 L s-1 km-2), and the frequency of events with greater than 3 times the median flow is 0.4 events / year, due to flow regulation and groundwater storage in pumice.

Prior to settlement native bush and scrub intercepted rainwater and allowed it to soak into the ground. The water filtered as it seeped through the ground and emerged as springs along the banks of the Waikato River. If the water level is not too high you can see a spring to the right of where you are. A significant volume of storm water no longer soaks into the ground but is directed through fast moving storm water channels. This can erode banks and areas around storm water outlets and wash sediment into waterways blocking light and making the water cloudy and dirty. Go to (visit link) to see modern storm water treatment systems being used to have better effects on our earth.

Please email the answers to these questions. Do not put them on your log.
1] What role does pumice play in the flow rate of the river?
2] At the published co-ordinates what discharges into the river?
3] Look at the water where you are then up river a little. Is there a difference in the clarity of the water?
4]What steps have been taken to minimize erosion at this point?
5] Name 3 major different benefits of the river for the city of Hamilton?
5] Post a photo [Optional]

Additional Hints (No hints available.)



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