Oral Presentation NCGRT/IAH Australasian Groundwater Conference 2019

Validating and scaling metered groundwater use data for the development of the Central Condamine groundwater flow model (423)

Leon L. M. Leach 1
  1. Dept Environment and Science, Dutton Park, QLD, Australia

This presentation describes the process used in pre-processing of groundwater use data for the MODFLOW unstructured grid (MFUSG) model for the Central Condamine and Tributaries. The objective was to validate and to scale groundwater use data to the model temporal and spatial scales where metered use data existed, and to derive and infill data where metered used data did not exist. The model domain is vast when compared to other alluvial systems in Queensland and covers an area of approximately 7,720 square kilometres with approximately 8,950 registered bores.  Of these there are approximately 3,340 bores with a water entitlement (licence).  Metering of some bores commenced in 1979, and to date 1,340 bores have been metered.  

Groundwater use data were captured at various time scales ranging from fortnightly, to annual and at different time intervals. Since metering commenced water use data were stored in a variety of systems ranging from initially paper to various database, and with a variety of index systems ranging from registration number (one to one) to property number (many to one)

One of the challenges was to derive groundwater use at the day scale for all 3,340 bores, for the period from 1960 to 2017. The first step in this process was to collate information on when and where the bores were drilled; and to establish if the bore is presently being pumped or when it ceased to be pumped.  The second step was to determine the likely extraction rate. .  For bore drilled before 1979, information on use and extraction rate were also obtained from property surveys and interviews with landholders.  

The next step was to establish time intervals when bores may have been pumped at the day scale. For most bores and particularly since 2005 bores, the granularity of meter use data at the annual scale precludes the identification of individual pumping sequences.  For some irrigation bores close to observation bores with equipped with data loggers, pumping sequences could be readily identified in the water level behaviour.  For more distant bores, pumping sequences were derived from an irrigation scheduling model.

Pre-processing software was developed using a hierarchal approach to derived daily groundwater use data with a data quality index identifying reliability and method. The index was used to assign weights for calibration purposes. Where possible, the quantum of the metered use was retained