Water tables and soil colour as an indicator of saturation in some soils of the Waikato, New Zealand

Abstract

Seasonal fluctuation in water tables in some alluvial soils in the Waikato was determined to establish time, depth and duration of saturation. Duration of saturation could then be related to soil colour to test whether colour could be used as an indicator of saturated conditions in these soils. The results confirmed that there were different watertable regimes between soil series and that there could be different depths and durations of water-table within a series. In the soils studied, colour can be used as a general indicator of whether or not saturated conditions have occurred. However, soil colour did not give any indication as to the time of year or continuous duration of a water table, or whether or not soil wetness had changed as a result of improved drainage. The results of this study highlight the dynamic water-table relationships between and within Waikato soils. For detailed land-use interpretations based on depth to a water table it is advisable to take watertable measurements at the site itself rather than to rely on assessments based on soil colour. When measurement is not practical, the worst conditions indicated by soil colour should be used for interpretations and planning soil management.