STUDY SITES FOR KARANGAKAHE There are three study sites suitable for school students: 1 A good site for students to investigate the geology of Karangahake rocks (see page 24). 2 Have a go at measuring water quality here (see page 25). 3 There is a prominent quartz vein here – making it a good location to discuss mining. Looking over the river, students will also be able to see the ‘windows’. to Paeroa hall and 2 parking railway tunnel Karangahake Reserve main car park and to Waihi toilets Ohinemuri River 2 2 River Survey 1 Karangahake Rocks Study The ‘Windows’ Track Karangahake Walkway (return the way you came) (follows river to Waikino Visitor Waitewheta River Centre) track under development 3 quartz vein in cliff Key: (short tunnel) = bridge Pumphouse N (no access) = walking track Please note: this map has not been drawn to scale. 2 = State Highway 2 = tunnel 23 IV. SITE 1 KARANGAHAKE ROCKS Background Information Millions of years ago, molten hot rock formed the volcanoes now known as the Coromandel Ranges. As the rock cooled, it developed cracks and crevices. Super hot water (230o-280oC) containing metallic minerals rose up from the hot rock deep below the mountains. As the water cooled it deposited gold, silver and a range of crystalline minerals including quartz, in these cracks and crevices - forming quartz ‘veins’. It is in these ‘veins’ that gold, silver and other minerals can be found. Where to go Any accessible stony patch along the Ohinemuri River will give productive rock hounding. The best area for schools is at the confluence of the Ohinemuri and Waitawheta Rivers (over the swing bridge and to your left). Keep conservation in mind and ask students to borrow a small representative collection (no more than six prized specimens) for observation and replacement. Look out for quartz crystals, which can also be found in the Ohinemuri and Waitewheta rivers. What to do 1. Collect your rock sample – choose smaller, flatter rocks. 2. Put on the safety glasses. 3. Wedge the rock between other rocks to stop rock fragments from flying off. 4. Strike the rock with the rock hammer. 5. Use a 3-D viewer or Waltex magnifier (8x magnification), holding the viewer close to the eye and the rock close to the end. View the rock in sun if possible, so you can see crystals sparkling. 6. Sketch or write down what you see. What you can expect to see Andesite and dacite Karangahake rocks are mainly andesite and dacite volcanic rocks, that erupted between 10 – 12 million years ago. They are grey with light coloured flexes through them. When broken, many crystals are seen in the dark grey background. The crystals, if light coloured (white or colourless) will be quartz and feldspar. Darker crystals, probably greenish, will be chlorite or pyroxene. Small shining specks may be pyrites. The other rocks are the same andecites and dacites but they have been changed by hydrothermal alteration. Quartz Quartz rocks are easy to identify. They are white, cream or pinkish with the crystals easily seen. An examination with the lens will show the crystal side shapes and pointed ends especially if holes and crevices in the rock are examined. When broken to expose a fresh face the quartz, fledspar and chlorite crystals will give a huge array of colours with good-sized cube crystals of iron pyrites (fool’s gold). 24 V. SITE 2 RIVER SURVEY Background Information Water pollution from mining In 1895, the Ohinemuri River was declared a ‘sludge channel’ devoid of all life. From 1895 to 1952 the Victoria Battery, capable of processing 200 tons of ore per day, dumped 11 million tons of waste into the river. The waste consisted predominantly of rock ‘flour’ as well as a wide variety of toxic chemicals. In addition, waste was also added from the Crown, Talisman and Woodstock Batteries. In its heyday, all town and domestic waste was also dumped into the river, most from specially built platforms. A highly valued Maori food resource of freshwater fish and eels was completely destroyed. The degradation continued unabated until mining ceased in the 1950s. Floods, so big that water flowed through the railway tunnel, carried the sludge to the Waihou River at Paeroa and out to the Firth of Thames. Recent exploration in the Firth has found gold and other minerals in the mud at Miranda that can be traced to Karangahake. With today's environmental protection laws such complete destruction of an ecosystem on such a large-scale would not happen. Improvements in water quality – the presence of trout Water quality in both the Ohinemuri and Waitawheta Rivers has improved to such an extent that the rainbow and brown trout fishery has become one of the most important to Auckland recreational fishers. In clear water conditions, trout can be spotted all along the walkway, particularly from the bridge over the Ohinemuri River between the Waikino railway station and the Victoria Battery. Rainbow trout are common and weigh about 1kg. Anglers occasionally catch brown trout weighing up to 5kg. Trout are a ‘valued’ introduced species and are used as indicators of good water quality. Smaller trout feed mostly on the larvae of freshwater insects such as caddis and mayfly, whereas the larger fish target smaller fish – probably native species of the whitebait family. 25 Water level surveys The Waikato Regional Council (Environment Waikato) regularly surveys waterways to ensure water quality is maintained. For example there are permanent rain gauges and water level recorders in the Karangahake area. Information on accumulated rainfall and river levels can be accessed via the internet. Visit the Environment Waikato websites given below before or after your visit – especially if there has been a significant rainfall event. Rainfall High rainfall events are www.ew.govt.nz/enviroinfo/riverlevelsandrainfall/rainfallmap exacerbated by rapid This web address takes you to a map of the Waikato. Click on the yellow runoff, due to lack of circle above Waihi for the latest rainfall data for the Waitekauri Catchment forest in the river (which feeds the Ohinemuri River). catchment. River Levels During the early days of www.ew.govt.nz/enviroinfo/riverlevelsandrainfall/riverlevelsmap the Victoria Battery On the map of the Waikato on this page – choose the yellow circle located operation, five acres of between Paeroa and Waihi. This will give you the latest river level readings for forest per day was cut to the Ohinemuri River. feed the kilns used to process the ore. The graph below shows the relationship between rainfall levels and river levels for the Ohinemuri River, Karangahake (28 March to 4 April 2001). Graph showing rainfall and resultant rise in river levels – Karangahake 2001 Rainfall and resultant rise in river levels - Karangahake 2001 River level rises in 300 response to rainfall. 16 river level 14 250 12 200 10 150 8 Rainfall (mm) 6 River Level (m) 100 rainfall 4 50 2 0 0 2 April 6:00am 3 April 9:00am 4 April 3:00am 1 April 3:00am 1 April 9:00pm 2 April 3:00pm 3 April 6:00pm 3 April 12:00am 1 April 12:00pm 30 March 6:00am 31 March 9:00am 28 March 9:00am 29 March 3:00am 29 March 9:00pm 30 March 3:00pm 31 March 6:00pm 28 March 6:00pm 31 March 12:00am 28 March 12:00am 29 March 12:00pm Date / Time 26 Now you’re there – Karangahake Reserve There is a water sampling kit suitable for schools available from Environment Waikato, Grey Street, Hamilton, Tel: 07-856-7184. Remember to return the kit as soon as possible after you have finished with it so that it can be used by other schools. Record your results on the recording sheet on page 29. What to do: • Make sure students have a copy of the recording sheet (page 29). Walk to the beach area downstream from the western end of the car park and measure: 1. water temperature, 2. water clarity, and 3. look for 'indicators' of good water quality. 1. Water temperature Use the thermometer provided in the kit. Hold the bottom of the thermometer about 10cm below the water surface for 2 minutes. The reading will be accurate to within two degrees. Check with another person before recording the temperature. 2. Water clarity Follow the instructions in the kit for the water clarity tube and the black disk equipment. Record both disk and tube readings. 3. ‘Indicators’ of Water Quality - River Animals Some insects and snails are water quality indicators. Use the nets to sample several stones, following instructions in the kit. Sort the catch out and record animals found, using the identification chart. Make a special record of any mayflies present as the record sheet suggests. All trout observations should be verified by two other people. Trout Both rainbow and brown trout live in the river and their presence is an indicator of good water quality. Spotting from the bank, you will not be able to identify the species. Trout are easily spotted when the water is clear and when there is not enough wind to ripple the surface of the water. Any of the bridges are good spotting places as well as sections of the walkway that gives views of smooth running water. Trout are solitary and large (up to 50 cm long, commonly 30 cm) and cruise slowly upstream. Other fish are smaller (except the odd eel) and may be in a shoal. Bullies will be darting around the rocks on the bottom. Common bully 27 Mayfly Mayflies (Deleatidium species) are used by biologists as indicators of high quality river water.