Over a third of New Zealand's fresh water is found in groundwater and derived from deep aquifers. These aquifers are a permeable layer of rock located between two impermeable layers or aquicludes. When a hole is drilled beyond the top aquiclude, the sealed pressure is released resulting in a naturally flowing artesian well. The recharging or refilling of these aquifers takes place in the higher mountain ranges such as the Southern Alps of the South Island. The source of water being rainfall or influent streams
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An Artesian Well in Marlborough, NZ located on the northern tip of the South Island. As a reliable source of water , wells like these enabled early communities to survive in dry regions.
(Image courtesy of
http://www.marlborough.govt.nz/Environment/Groundwater.aspx )
Due to New Zeland's heavy dependence on agricultural exports, farmers were forced to clear forests even on the slopes near the mountains. With over 22 hectares of plowed farmland this equated to the depletion of nearly 65% of original forestry. New Zealand's regional podzolization resulted in deep sub soils with a thin top soil and abundant leaf litter. With the absence of deep rooted Podocarp trees, biogenic transport accelerated and thus destabilized the soil. This lowered the cation exchange capacity of the soil and left the grasslands infertile.
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Map of Erosion Susceptible Regions in New Zealand. It is important to note the greater weakness to erosion along steeper slopes due to stronger gravitational impact.
(Image courtesy of http://www.seafriends.org.nz/enviro/soil/soilnz.htm)
Aerial view of dark green forest, light green man made pasture and the pale green areas spotted with bare soil. The lack of stable roots and healthy top soil resulted in the creep and biogenic transport of soil down into gullies and rivers. (Image courtesy of http://www.teara.govt.nz/en/natural-environment/4/1)
Map of Soil Orders of the North Island. Unlike the South Island, notice the large presence of pumice soil as a result of volcanic ash from the Taoupo Volcanic Zone.
(Image Coutesy of http://www.mfe.govt.nz)
New Zealand's climate ranges from humid subtropical in the north to cooler more seasonal temperatures with frequent rain in the south. These conditions helped to form Inceptisols, Spodosols, and Ultisols, the three most common orders of soil in New Zealand. Inceptisol is found along the flood plains east of the Southern Alps. Spodosol is found around forested or previously forested areas. This is due to the higher acidity from semi-coniferous leaf litter and the consistent rainfall that leaches minerals from the O horizon. Ultisol is similar to Oxisol in its high weathering and red coloration. It is found on the warmer North Island.
Map of Soil Orders of the South Island. The majority of the South Island is covered with spodosols formed by pedzolization. (Image Courtesy of http://www.mfe.govt.nz)
Sources:
Dr. Casey Allen
www.mfe.govt.nz,
www.teara.govt.nz,
www.soils.landcareresearch.co.nz
www.waternz.org.nz
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