University of Technology, Sydney. Faculty of Science.NO FULL TEXT AVAILABLE. Access is restricted indefinitely. The hardcopy may be available for consultation at the UTS Library.NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- Statistical analyses of borehole hydrographs reveal a new understanding of the
spatial distribution of hydrogeological properties throughout the multi-layered
alluvial aquifer system of the Lower Namoi Valley, NSW, Australia.
Principal component analysis and k-mean clustering divided the Narrabri Formation
hydrographs into 6 clusters, and the Gunnedah Formation hydrographs into 7
clusters. The clusters relate to variations in- recharge and extraction throughout the
Lower Naomi Valley.
A comparison of rainfall residual mass curves with the water level trends displayed
in the borehole hydrographs shows that there is a strong correlation between the
water level fluctuations and the rainfall history. The analysis also indicates that the
irrigation extractions are in balance with recharge near the southern, northern and
western boundaries, but in the southeast comer and throughout much of the central
region of the Lower Namoi Valley there are numerous areas where extractions
exceed recharge.
A comparison of the results from the statistical analyses with two previous studies, a
MODFLOW model of the aquifers and a chemical investigation of the aquifer
chemistry, highlights where there is agreement on recharge and groundwater
movement, but it also shows that there are regions where the various approaches
provide a different or unique understanding of aquifer processes
