Quality control and quality assurance of Hawke's Bay rainfall recharge measurements : 2011-2014

(Inc. GST)
(Ex. GST)
Write a Review

White, P.A.; Lovett, A.P.; Gordon, D. 2017 Quality control and quality assurance of Hawke's Bay rainfall recharge measurements : 2011-2014. Lower Hutt, N.Z.: GNS Science. GNS Science report 2016/16 21 p.; doi: 10.21420/G28G6P

Abstract: The Hawke’s Bay Regional Council (HBRC) has installed a network of five groundwater recharge measurement sites in the region. These sites have been installed as part of an investigation programme in collaboration with GNS Science and the National Institute of Water and Atmospheric Research’s Waterscape Research Programme. Four sites measure rainfall recharge (i.e., recharge through dry land, which is non-irrigated soil) and one measures recharge from rainfall and irrigation. This report describes quality assurance and quality control (QA/QC) checks on data collected at the four rainfall recharge sites in the period 2011 – 2014. These sites were located over the Heretaunga Plains aquifer system (i.e., at Bridge Pa, Maraekakaho and Substation) and the Ruataniwha Plains at Ashcott Road. Each installation consists of three lysimeters, a ground-level tipping-bucket rainfall recorder and a ground-level rainfall storage gauge. In addition, rainfall recharge measurements at these sites were supplemented with climate observations that were available at, or in the immediate vicinity of, the rainfall recharge sites. Monthly QA/QC field checks were completed by HBRC, including: site and instrument maintenance; checks of data logger function; and completion of an ‘Environmental Monitoring Inspection Sheet’. Standard HBRC QA/QC data procedures were applied, including: removal of test tips; verification of data, with identification of false data or missing data; and quality-coding of the data. Continuous time-series data of rainfall recharge and ground-level rainfall at daily intervals were assembled with further QA/QC checks including identification of: dataset gaps, outliers and observational drift over time. Continuous datasets were assembled by filling gaps in the recorded data with best-estimates of environmental variables based on observations at nearby sites. These time series are provided on a CD that is attached to this report. The rainfall recharge ratio, i.e., total rainfall recharge divided by total ground-level rainfall was greatest (0.47) at the Substation site and least (0.22) at the Bridge Pa site. This difference is likely due to coarser soils at the Substation site, which allow greater infiltration of rainfall. Rainfall recharge varies considerably between seasons at all sites. Typically, rainfall recharge is zero, or very low, in summer and relatively high in winter. (auth)