2.1.3.2 Observed data

The observed data for the Clarence-Moreton bioregion are mainly from the Queensland and NSW state groundwater databases (Bioregional Assessment Programme, Dataset 2; Bureau of Meteorology, Dataset 1; NSW Hydstra and NSW WDTF) collected by the Bureau of Meteorology. As data collection ceased in November 2013, data received after November 2013 were not included in the analysis. Only bores with enough data to determine screen intervals or bore depth were used in the analysis (Table 10) as these data are necessary to assign a bore to particular aquifers. In the absence of bore screen data, the bore was assigned to an aquifer based on the depth of the bore if this information was deemed reliable and plausible. Seven screen codes are used to indicate different bores in terms of their spatial relationship with a particular aquifer. They are:

I: bores with screen intervals inside the aquifer
T: bores with a screen top inside the aquifer
B: bores with a screen bottom within the aquifer
E: bores with screen intervals penetrating the entire aquifer
BOI: bores with their bottom inside the aquifer although without screen information in the database
DS: aquifer assignment for a bore sourced directly from the state database where the bore is only open to a single aquifer
DM: aquifer assignment for a bore sourced directly from the state database where the bore is screened to multiple aquifers.

The alluvium, Main Range / Lamington Volcanics and Woogaroo Subgroup represent the three most targeted aquifers with 3536, 921 and 868 associated bores, respectively. The mean of bore depths is less than 50 m and the 90th percentile of bore depth is around 120 m (Figure 21). Therefore, most bores in the Clarence-Moreton bioregion are relatively shallow with respect to the basin basement depth (2–4 km). Most bores are screened to either the alluvium or the outcrops of underlying bedrock aquifers. The shallow reach of bedrock bores is also demonstrated by their spatial distribution along the aquifer boundary. Figure 22 to Figure 28 display the spatial distribution of bores with construction information in major aquifers.

Figure 21 Histogram showing the distribution of bore depths in the Clarence-Moreton bioregion

The inset shows the corresponding statistical summary. Three bores RN22500, RN75903 and RN124727, with respective depths of 1202 m, 805 m and 518 m, have been excluded from the plot for increased figure resolution.

Data: Bureau of Meteorology (Dataset 1), Queensland Department of Natural Resources and Mines (Dataset 3)

Table 10 Number of bores with screen and/or depth information grouped by aquifers

The depth column presents the depth range of bores associated with a specific aquifer. Bores with different screen codes have been counted separately.

Major stratigraphic unit	Number of bores: I	Number of bores: T	Number of bores: B	Number of bores: E	Number of bores: BOI	Number of bores: DS	Number of bores: DM	Total	Depth range (m)
Alluvium	568	260	30	173	89	2380	36	3536	1.3–45
Main Range / Lamington Volcanics	610	75	35	126	0	74	1	921	3.5–186
Grafton Formation: Rapville Member	75	2	19	25	0	0	0	121	9.8–168
Grafton Formation: Piora Member	134	11	10	31	0	0	0	186	9.1–490
Orara Formation: Bungawalbin Member	13	0	1	3	0	0	0	17	16–111
Orara Formation: Kangaroo Creek Sandstone Member	23	0	3	5	0	0	0	31	10.3–97
Walloon Coal Measures	70	3	7	17	1	243	12	353	3.7–518
Marburg Subgroup (undifferentiated)	0	0	0	1	0	40	6	47	14–261
Marburg Subgroup: Koukandowie Formation	30	10	1	3	0	116	8	168	9.1–305
Marburg Subgroup: Gatton Sandstone	50	22	2	58	5	284	43	464	4–432.9
Woogaroo Subgroup	36	10	11	66	2	704	39	868	4.5–1202.7

Screen codes are: (I) bores with screen intervals inside the aquifer; (T) bores with a screen top inside the aquifer; (B) bores with a screen bottom within the aquifer; (E) bores with screen intervals penetrating the entire aquifer; (BOI) bores with their bottom inside the aquifer although without screen information in the database; (DS) aquifer assignment for a bore sourced directly from the state database where the bore is only open to a single aquifer; (DM) aquifer assignment for a bore sourced directly from the state database where the bore is screened to multiple aquifers.

Data: Bureau of Meteorology (Dataset 1), Queensland Department of Natural Resources and Mines (Dataset 3)