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Wetlands help the surrounding environment by acting as a huge living sponge. So why would you drain them?

Wetlands can hold vast amounts of water that seep out during drier periods stopping rivers from drying up, while in floods they abosorb excess water. Wetlands act as huge water filters helping to maintain good water quality.

Yet across the Taranaki region wetlands are being drained at an alarming rate to make way for pasture. Wetland drainage has a slow and cumulative effect on the supply of groundwater by lowering the water table in the surrounding land, and the result is that many shallow wells that used to provide water year round now dry up in summer when water is needed the most. Similar effects are seen in stream flows during summer dry spells, as they are mainly feed by groundwater. 

Value of wetlands:

  • Retains the groundwater on the land when it is needed most.
  • Directing farm runoff through one or a series of wetlands, will contribute towards cleaner water in streams and rivers, particularly if this is done on a whole of catchment basis.
  • Treats and cleans runoff. Wetlands are a natural filter system for nutrients, heavy metals, silt, and many other types of contaminants that enter them via runoff.
  • Helps prevent topsoil from washing away.
  • Buffers flood flows by absorbing water and releasing slowly, protecting land from flood damage;
  • Wetlands are carbon sinks. Peat stores carbon.
  • Supports rich biodiversity (plants, birds, fish, and insects). Important for survival of many threatened native fish species (galaxids, eels).
  • Source of traditional medicine and food.
  • Aesthetic and recreational.

Adverse effects of wetland and land drainage:

  • Drainage causes a decline in the level of the water table leading to less water available in shallow wells and bores and this can lead to wells and bores running out of water. As a result, many farmers are now forced to drill deeper for water.
  • Drainage also affects stream flows, in that summer low-flows arrive earlier in the season, are lower than they used to be, and last longer. These effects lead to the straining of surface water supplies during peak demand period (summer).

Benefits of wetland preservation & enhancement as a whole of catchment approach:

  • Wetlands provide a natural filter system for nutrients and bacteria (E.coli) runoff from farms.
  • Wetlands naturally occur in low spots so they lend themselves to receiving runoff from surrounding land
  • Preserving Wetlands maintains higher water table level in surrounding land during summer-autumn which effectively provides more reliable water supply to shallow wells and bores.
  • Preserving Wetlands can delay the arrival of stream low flows, to later in the season. Low flows are higher, and not as long lasting.
  • Wetlands can be reconstructed, but it is better to retain and enhance existing wetlands.
  • In some cases there is funding available to enhance a wetland. (see Taranaki Regional Council.)

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