Properties and Distribution of Soils on the Ruataniwha Plains, Hawke’s Bay: A New Approach Integrating Classical and Digital Mapping Techniques
Hainsworth, S. B. (2011). Properties and Distribution of Soils on the Ruataniwha Plains, Hawke’s Bay: A New Approach Integrating Classical and Digital Mapping Techniques (Thesis, Master of Science (MSc)). University of Waikato, Hamilton, New Zealand. Retrieved from http://hdl.handle.net/10289/6129
Permanent Research Commons link: http://hdl.handle.net/10289/6129
This thesis is about soil properties and their spatial distribution on the Ruataniwha Plains in central Hawke’s Bay. The Ruataniwha Plains are situated between the Ruahine Ranges in the west, Takapau in the south and Waikpukurau in the east. Soil moisture deficits are common in the Ruataniwha Plains and the underlying aquifers are currently fully allocated for irrigation. The central Hawke’s Bay irrigation scheme (the scheme) has thus been proposed. The Ministry of Agriculture and Forestry has recently made available the ‘Irrigation Acceleration Fund’ to “support the potential for irrigated agriculture to contribute to sustainable economic growth throughout New Zealand”. The Ministry for the Environment has also recently published the National Policy Statement on Fresh-Water Management (2011), which regulates to ensure that not only are life-supporting capacities related to water maintained, but also to ensure that water quality is improved. A sufficient level of detail about the properties and spatial distribution of soils in the Ruataniwha Plains is therefore required to evaluate the potential changes in productivity, versatility and environmental impacts from the scheme. Although information about the spatial distribution of soils in the Ruataniwha Plains is available at 1:50,000, more detailed soil information not currently available, will be required at the feasibility, resource assessment, concept design and implementation stages of the scheme (1:25,000–1:5,000, respectively). Information about the physical, chemical and hydrological properties of the soils of the Ruataniwha Plains will also be required, but is currently very limited in availability. A land systems model has been developed. Existing information about the properties of the soils of the Ruataniwha Plains has been reclassified using the New Zealand Soil Classification and S-Map systems, thus enabling correlation to national datasets about soils with similar properties. Correlation to the national SMap database has also provided new estimates of soil properties using pedotransfer functions that can be rapidly updated nation-wide. By combining legacy soils data and that derived from the S-Map database, a new soils-based land use capability (LUC) map and associated database have been developed. The LUC data can be linked to maps of any scale, provided the soil map units are classified using the S-Map family and sibling nomenclature. The new LUC map assumed that all land had been artificially drained where necessary and incorporated data about the spatial distribution of currently irrigated farms in the Ruataniwha Plains. Drainage and soil moisture deficit limitations were removed thus resulting in upgrades of LUC units in the relevant areas of the LUC map. The resultant LUC information includes estimates of productivity for each LUC unit. The total productivity of the soils of the Ruataniwha Plains, in the current (2011) scenario was calculated. A second, hypothetical, scenario was developed, where all soils in the Ruataniwha Plains were assumed to be irrigated, and the total productivity of all of the soils in the Ruataniwha Plains under this future scenario was compared with the current (2011) scenario, showing an increase in productivity. The value of this process is the demonstration of a viable method for comparisons of the impact of irrigation on general versatility and productivity. Information about soil properties derived from the reclassification of the original soils information into the nomenclature of the S-Map and LUC systems was used to evaluate the soils of the Ruataniwha Plains for their versatility for orchard cropping, and their suitability for the application of farm dairy effluent. A new 1:25,000 scale digital soil map of the Ruataniwha Plains was produced. Landforms were spatially delineated at 1:25,000 using aerial photograph interpretation. Flow-direction, topographic wetness index and curvature co-variate layers were produced from a LiDAR-based 6.25m DEM. The co-variate layers were reclassified into landform components within landforms within field-based training windows, then extrapolated across the Ruataniwha Plains using the 1:25,000 landforms map. The training windows were also used to validate previously determined soil-landscape relationships. These soil-landscape relationships were then applied to the landform-landform component map to produce the final soil map.
University of Waikato
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