The predictions of hydrological change associated with the __additional coal resource development__ are shown in the boxplots in Figure 18 to Figure 26. In these figures, the model nodes are grouped for different river sections and tributaries. Nodes are ordered from downstream to upstream. The tributary grouping ‘lower Namoi’ includes tributaries (excluding the anabranches) that join the Namoi River from nodes 1 to 18 plus tributary nodes 19 and 20. The tributary grouping ‘mid Namoi’ includes Maules Creek and the tributaries that join the Namoi River between node 24 and node 30. The tributary grouping ‘Mooki’ includes nodes on the Mooki River and its tributaries. Within this grouping, the tributaries of the Mooki River have a grey background shading. The tributary group labelled ‘upper Namoi’ includes all the modelled tributaries of the Namoi River that are upstream of Mooki River. Refer to Figure 5 in Section 2.6.1.3 for a schematic depiction of the model nodes and the network topology.

### Annual flow

Figure 18 shows the changes to the __annual flow__ (AF) at the 54 model nodes. The biggest percentage reductions occur in some of the small tributaries of the Namoi and Mooki rivers and range up to a median *pmax* of 23% at node 25 (Merrygowen Creek). Four model nodes have reductions in median *pmax* that exceed 8%. All of these have catchment areas of less than 100 km^{2}. There are tightly constrained distributions of *pmax* values around these median values at all the heavily affected nodes. Apart from these four model nodes there is little impact on *pmax* in the other nodes in the subregion.

The largest reductions in median *amax* are located in the lower Mooki River and in the middle reaches of the Namoi River and tend to increase with distance downstream as far as node 13. Below node 13 the impact on *amax* is lessened as some of the flow is diverted into Pian and Gunidgera creeks. As a __consequence__, the biggest effects are at nodes 13 and 18 and result in median changes of around 7 GL/year, which represent about 0.2% of the baseline flow. A significant proportion of this median reduction (4 GL/year) originates in the Mooki River (node 33 and above).

For the nodes with the biggest changes in *pmax*, the median year at which maximum hydrological changes occur is either 2028 or 2034 for the tributaries of the mid Namoi River (nodes 22 and 25), but 2058 for node 34 (a tributary of the Mooki River) and node 54 (a tributary of Lake Goran). There is relatively little uncertainty in these dates. The maximum hydrological changes in the Namoi River itself tend to occur in 2028.

*amax* = maximum raw change; *pmax* = maximum percent change; *tmax* = year of maximum change; NI, no impact

Numbers above the top panel are the median of the best 300 replicates under the baseline for the year corresponding to the median *tmax*. In each boxplot, the bottom, middle and top of the box are the 25th, 50th and 75th percentiles, and the bottom and top whiskers are the 5th and 95th percentiles.

Refer to Figure 5 for location of model nodes.

Data: Bioregional Assessment Programme (Dataset 1)

### Daily streamflow at the 99th percentile

Figure 19 shows the changes to the daily flow rate at the 99th percentile (P99) at each model node. The biggest changes in *pmax* occur at the same four locations with the biggest effect on __AF__. For P99 the median *pmax* values for these four nodes exceed 8% and range up to 18% for nodes 22 (Back Creek) and 25 (Merrygowen Creek). At most of these sites there is a smaller relative spread of *pmax* values than there is for AF. At most of the affected nodes, the percentage reduction in P99 is smaller than the percentage reduction in AF.

In the heavily affected nodes, the year of maximum change in P99 tends to correspond with the year of maximum change in AF, with the exception that it occurs (2028) earlier in node 25. However, in the nodes of the Namoi River and its anabranches the maximum change tends to be delayed until the early 2040s.

*amax* = maximum raw change; *pmax* = maximum percent change; *tmax* = year of maximum change; NI, no impact

Numbers above the top panel are the median of the best 300 replicates under the baseline for the year corresponding to the median *tmax*. In each boxplot, the bottom, middle and top of the box are the 25th, 50th and 75th percentiles, and the bottom and top whiskers are the 5th and 95th percentiles.

Refer to Figure 5 for location of model nodes.

Data: Bioregional Assessment Programme (Dataset 1)

### Interquartile range

Figure 20 shows the changes to the interquartile range (IQR) of daily flow rate at each model node. The changes in IQR due to __additional coal resource development__ are always reductions. This implies that the difference in flow rates between high flows (the 75th percentile of daily streamflow) and low flows (the 25th percentile of daily streamflow) is reduced, mostly likely through a decrease in the 75th percentile. The patterns of change are similar to those of __AF__ (Figure 18) and P99 (Figure 19). The biggest reductions in median *pmax* occur at nodes on small tributaries of the mid Namoi River, and include reductions of more than 60% at nodes 22 (Back Creek), 25 (Merrygowen Creek) and 27 (Bollol Creek).

*amax* = maximum raw change; *pmax* = maximum percent change; *tmax* = year of maximum change; NI, no impact

Numbers above the top panel are the median of the best 300 replicates under the baseline for the year corresponding to the median *tmax*. In each boxplot, the bottom, middle and top of the box are the 25th, 50th and 75th percentiles, and the bottom and top whiskers are the 5th and 95th percentiles.

Refer to Figure 5 for location of model nodes.

Data: Bioregional Assessment Programme (Dataset 1)

### High-flow days

Figure 21 shows the changes to __high-flow days__ (FD) at each model node. Once again, the largest reductions in the number of high-flow days occur in the small tributaries of the Namoi River as well as in tributaries of the Mooki River and Lake Goran. The biggest change is a maximum reduction in the median number of high-flow days by 33 days per year at node 22 (Back Creek). Six nodes have median reductions in *amax* of more than 5 days per year. However, there is much greater uncertainty around changes in the number of high-flow days (and in the timing of the maximum changes) than there is for changes in __AF__. Along the Namoi River, __FD__ is reduced by no more than 1 day per year.

*amax* = maximum raw change; *pmax* = maximum percent change; *tmax* = year of maximum change; NI, no impact

*tmax*. In each boxplot, the bottom, middle and top of the box are the 25th, 50th and 75th percentiles, and the bottom and top whiskers are the 5th and 95th percentiles.

Refer to Figure 5 for location of model nodes.

Data: Bioregional Assessment Programme (Dataset 1)

### Daily streamflow at the 1st percentile

Figure 22 shows the changes to the daily flow rate at the 1st percentile (P01) at each model node. Reductions in median *pmax* of more than 30% are predicted in many of the tributary nodes, including all nodes with large reductions in high-flow characteristics. Reductions in median *pmax* of 100% are predicted for several mid Namoi and Mooki tributary nodes. These cases are representative of a particular year in a replicate for which there is a non-zero 1st percentile of baseline flow, but the 1st percentile of __CRDP__ flow is zero. In the main channel of the Namoi River below its junction with the Mooki River, reductions in P01 are predicted for every node, but do not exceed 5%.

The timing of the maximum changes tends to be later for P01 than for the high-streamflow __hydrological response variables__. The median *tmax* for P01 occurs in or later than 2044 at all of the heavily affected nodes except for node 27 (2034).

By comparison to the three flux-based high-streamflow hydrological response variables (__AF__, IQR and P99), P01 tends to have greater uncertainty – as shown by a large interquartile range relative to the median response – for both *pmax* and *tmax*.

*amax* = maximum raw change; *pmax* = maximum percent change; *tmax* = year of maximum change; NI, no impact

*tmax*. In each boxplot, the bottom, middle and top of the box are the 25th, 50th and 75th percentiles, and the bottom and top whiskers are the 5th and 95th percentiles.

Refer to Figure 5 for location of model nodes.

Data: Bioregional Assessment Programme (Dataset 1)

### Zero-flow days

Figure 23 shows the increases in the annual number of zero-flow days (ZFD) due to __additional coal resource development__. All of the model nodes along the Namoi River are perennial in both the __baseline__ and __CRDP__ simulations and therefore show no impact on ZFD. The only model nodes with changes that exceed one or more of the specified thresholds of hydrological change (provided in Section 8.1.4 of companion submethodology M06 (as listed in Table 1) for surface water modelling (Viney, 2016)) are some of the small tributary nodes of the Namoi River and the nodes of the Mooki River. The largest predicted changes in ZFD are increases of 148 and 189 days/year at nodes 22 and 27. Changes in median *amax* exceed 40 days/year in six other nodes in tributaries of the mid and lower Namoi River and in the Mooki River. However, there is considerable uncertainty in these projections.

Despite this uncertainty in the amount of change, its timing is relatively tightly constrained for three of the most heavily affected nodes (nodes 22, 25 and 27) with median *tmax* falling between 2028 and 2035. However, there is less certainty in *tmax* at other affected locations where the median tends to occur much later.

*amax* = maximum raw change; *pmax* = maximum percent change; *tmax* = year of maximum change; NI, no impact

*tmax*. In each boxplot, the bottom, middle and top of the box are the 25th, 50th and 75th percentiles, and the bottom and top whiskers are the 5th and 95th percentiles.

Refer to Figure 5 for location of model nodes.

Data: Bioregional Assessment Programme (Dataset 1)

### Low-flow days

Figure 24 shows the increases in the annual number of low-flow days (LFD) due to __additional coal resource development__. There are substantial predicted increases in *amax* in many tributary nodes. The biggest predicted changes are median increases of more than 300 days/year at nodes 22 (Back Creek), 25 (Merrygowen Creek) and 27 (Bollol Creek), and there are seven other tributary nodes with median increases exceeding 50 days/year. The biggest changes along the Namoi River are increases of 3 days/year at nodes 18, 26 and 32.

As is the case with ZFD, there is less uncertainty in *tmax* and earlier median *tmax* values at nodes 22, 25 and 27 than at other heavily affected nodes. For two nodes (nodes 31 in Driggle Draggle Creek and node 37 on the Mooki River) the median *tmax* does not occur until the 2090s.

*amax* = maximum raw change; *pmax* = maximum percent change; *tmax* = year of maximum change; NI, no impact

*tmax*. In each boxplot, the bottom, middle and top of the box are the 25th, 50th and 75th percentiles, and the bottom and top whiskers are the 5th and 95th percentiles.

Refer to Figure 5 for location of model nodes.

Data: Bioregional Assessment Programme (Dataset 1)

### Low-flow spells

Figure 25 shows the changes in low-flow spells (LFS) due to __additional coal resource development__. Nodes with large *amax* for LFS are the same as those for LFD and are predominantly in tributaries of the Namoi River. Median *amax* values for LFS range up to 31 spells/year at node 22 (Back Creek). In the Namoi River, no node has a median *amax* value exceeding 1 spell/year. No node has a decrease in the number of LFS, although some do have negative *amax* values at the 5th percentile. These reductions in LFS result when multiple spells coalesce into a single large spell.

There is considerable uncertainty in the projections of both *amax* and *tmax* in Figure 25, although most median *tmax* values occur before 2050.

*amax* = maximum raw change; *pmax* = maximum percent change; *tmax* = year of maximum change; NI, no impact

*tmax*. In each boxplot, the bottom, middle and top of the box are the 25th, 50th and 75th percentiles, and the bottom and top whiskers are the 5th and 95th percentiles.

Refer to Figure 5 for location of model nodes.

Data: Bioregional Assessment Programme (Dataset 1)

### Longest low-flow spell

Figure 26 shows the maximum changes to the length of the longest low-flow spell (LLFS). The changes in the LLFS are very similar to those in LFD, with the same three mid Namoi nodes being most affected. The longest low-flow spell is projected to increase in length by nearly 200 days at node 27 (Bollol Creek) and by more than 20 days at nine other small tributary nodes. The biggest change in the Namoi River is an increase of 10 days at node 5, but elsewhere along the Namoi River, the longest low flow spells do not increase by more than 2 days.

*amax* = maximum raw change; *pmax* = maximum percent change; *tmax* = year of maximum change; NI, no impact

*tmax*. In each boxplot, the bottom, middle and top of the box are the 25th, 50th and 75th percentiles, and the bottom and top whiskers are the 5th and 95th percentiles.

Refer to Figure 5 for location of model nodes.

Data: Bioregional Assessment Programme (Dataset 1)