The Northern Territory Department of Environment and Natural Resources have developed integrated surface-groundwater models to better inform management decisions relating to water resource allocation.

Due to the remote nature of the Northern Territory (NT) and resultant site access issues, data available for the construction of these models is spatially sparse, resulting in significant interpolation of hydrological and hydrogeological features.

In order to increase resolution of the hydraulic gradient and better define the interface between surface and groundwater resources, a longitudinal survey was undertaken of the primary channel thalweg for both the Roper and Katherine-Daly Rivers. Project objectives included determination of river bed height to an accuracy of ±0.200 m Australian Height Datum (AHD) along the non-tidal length of both rivers.

With poor river access, no survey control points (benchmarks) along most of the survey area and no communication network, conventional Real Time Kinematic (RTK) Differential Global Navigation Satellite System (GNSS) techniques using a base station over a known point would be prohibitively expensive and time consuming.

Utilising a new satellite based precise point positioning correction service for GNSS survey; a longitudinal section was completed for both rivers within the required accuracy limits and within a suitable timeframe and budget without the need for establishing a dense network of survey control points to achieve required project accuracies.

This paper will provide an overview of the technology, and the two different techniques that were used to undertake each survey.