Report: TR 2005/61

Author: Robert Rout, Aqualinc Research Ltd. (formerly Lincoln Environmental)

Abstract

This study forms part of Environment Waikato's (EW) on-going commitment to the sustainable management of water resources in the Waikato region. This commitment includes the investigation of practical, economic and social methods to improve water use. It follows on from earlier studies establishing crop water requirements, irrigation efficiencies in the Franklin area and a review of the resource consent process.

Irrigation is a major consumptive use within the region, much of which is allocated for irrigation of pasture on dairy farms. It has been widely adopted on dairy farms in the Reporoa basin of the south Waikato, as a means to achieving sustainable increases in farm production. The area is prone to summer drought due to a combination of lower rainfall and low waterholding pumice soils. Surface water resources have been allocated for irrigation from the Waikato River and tributary streams. There are at least 28 farms in the basin with a combined irrigated area of more than 2,500 ha and daily allocation in excess of 100,000 cubic metres per day (m³/d).

The purpose of the study was to investigate current levels of irrigation efficiency on dairy farms and the costs and benefits of improvements in efficiency. It was based on a sample of 12 irrigated farms in the Reporoa basin. The sample included the range of commonly adopted irrigation methods, these were; centre pivot (3), K-lines (2), long-laterals (4) and travelling gun irrigators (3). The three farms with centre pivots also used other methods (K-line, long-lateral and travelling irrigators) to irrigate areas not covered by the pivot. The farms had combined effective and irrigated areas of 1,800 and 1,100 hectares respectively, and total water allocation equivalent to 55,180 m³/d.

The study is based on a farm system approach, utilising a variety of data sources and analytical methods. A key element was the farm survey, which collected information on irrigation methods, cost and management as well as farm productivity. Other information sources included climate data (Reporoa, Rotorua and Taupo), soils data (waterholding characteristics), water use records and irrigation pump electricity consumption (for calculation of seasonal water use).

Investigating Dairy Farm Irrigation Efficiency in the Reporoa Basin [PDF, 677 KB]