Assessment of resources and modelling of groundwater systems usually require quantification of groundwater abstraction (use). With increasing frequency, water takes are metered and data becoming available. However, there is often a disconnect between the data required for an assessment and that which is available. Furthermore, data for smaller (often permitted or unconsented) takes does not exist.
We will outline two approaches for quantifying groundwater abstraction. The first approach estimates permitted groundwater use based on available permit information, land cover, agricultural statistics, and other data (including probably source of water). The second approach uses consent information and converts this to a likely actual take based on climate, crop types, and irrigated areas.
These approaches have been used to quantify groundwater takes in the face of missing or imperfect data. In one case study, the results have informed policy decisions; in other cases, the results have been used as inputs to a groundwater model.
A more innovative approach to making use of data is often needed to make use of available information and enable us to understand groundwater use, particularly in cases where data are limited or non-existent.