Daly
Water resources and systems

Introduction

The following set of notes provides consolidated reports for each of the water stores and systems within the Daly region during the 2011–12 year. The water stores and systems included in the region are shown in Figure 1.

For more information about the region, please refer to the General description section of the 'Contextual information'.


Figure 1  Schematic diagram of the water stores and systems within the Daly region
Figure 1  Schematic diagram of the water stores and systems within the Daly region


Information on all water flows to and from each water store and system are presented in this note, including between-store flows and transfers that are not presented in the water accounting statements. The between-store flows and transfers that occur in the region are presented in Figure 2.

The numbers on the diagram refer to the line item numbers in the water store notes. For each between-store flow, there are two line item numbers: one refers to flow out of a water store and the other refers to flow into a water store.


Figure 2  Schematic diagram of between-store flows that occur within the Daly region. Line item numbers are provided next to the flows.
Figure 2  Schematic diagram of between-store flows that occur within the Daly region. Line item numbers are provided next to the flows.


The between-store flows and transfers (Figure 2), which are eliminated from the region's water accounting statements, are shown in italics throughout the following set of notes.

Surface water

Background

A description of the Daly region's surface water resources is provided in the Surface water section of the 'Contextual information'.

Water in store

While good information exists on water movement to and from the surface water store (see following section on 'Changes in water store'), only limited data are available for the volume of water in the store. No value could be estimated for the volume in rivers, indicated by a dash ('–') for line item 1.2 in Table 1, which is the largest component of the surface water asset. The volume of water in lakes and wetlands (line item 1.4) also could not be quantified due to a lack of available data.

The Statement of Water Assets and Water Liabilities for the surface water store (Table 1) shows that total surface water liabilities decreased marginally during the 2011–12 year in the Daly region. Consequently, net water assets increased slightly during the year.


Table 1  Statement of Water Assets and Water Liabilities for the surface water store
Water assets Volume at 30 June 2012
(ML)
1 Surface water  
1.1 Storages 500
1.2 Unregulated river
1.4 Lakes and wetlands
Total surface water assets 500
   
Water liabilities  
5 Surface water liability  
5.1 Surface water allocation remaining 3,549
5.2 Surface water allocation remaining – urban water system 3,010
Total surface water liabilities 6,559
   
Opening net water assets (6,076)
Change in net water assets 17
Closing net water assets (6,059)


Changes in water store

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the surface water store are provided in Tables 2 and 3 respectively.


Table 2  Statement of Changes in Water Assets and Water Liabilities for the surface water store
Water asset increases 2011–12 volume
(ML)
9 Surface water increases  
9.1 Precipitation on surface water 32,132
9.3 Groundwater discharge 1,219,000
9.4 Runoff to surface water 30,590,000
9.6 Overbank flood return to river channel
9.9 Discharge from urban water system 114
Total surface water increases 31,841,246
   
Water liability decreases  
13 Surface water liability decreases  
13.1 Adjustment and forfeiture of surface water allocation 3,137
13.2 Adjustment and forfeiture of surface water allocation – urban water system 1,070
Total surface water liability decreases 4,207
   
Water asset decreases  
17  Surface water decreases  
17.1 Evaporation from surface water 33,137
17.2 River outflow from the region 9,698,000
17.3 Leakage to groundwater 65,000
17.5 Overbank flood spilling
17.6 Surface water diversions – other statutory rights 4,338
Total surface water decreases 9,800,475
   
Water liability increases  
21 Surface water liability increases  
21.1 Surface water allocation announcements 3,651
21.2 Surface water allocation announcements – urban water system 3,456
Total surface water liability increases 7,107
   
Balancing item—surface water 22,037,854
   
Change in net water assets 17


Table 3  Statement of Water Flows for the surface water store
Water inflows 2011–12 volume
(ML)
9 Surface water inflows  
9.1 Precipitation on surface water 32,132
9.3 Groundwater discharge 1,219,000
9.4 Runoff to surface water 30,590,000
9.6 Overbank flood return to river channel
9.9 Discharge from urban water system 114
Total surface water inflows 31,841,246
   
Water outflows  
17 Surface water outflows  
17.1 Evaporation from surface water 33,137
17.2 River outflow from the region 9,698,000
17.3 Leakage to groundwater 65,000
17.5 Overbank flood spilling
17.6 Surface water diversions – other statutory rights 4,338
17.11 Entitled diversion of allocated surface water to users 562
17.12 Entitled diversion of allocated surface water to urban water system 2,355
Total surface water outflows 9,803,392
   
Balancing item—surface water 22,037,854
   
Opening water storage 500
Add/(Less): Change in water storage 0
Closing water storage 500


A schematic diagram representing all the inflows and outflows associated with the surface water store in the Daly region is provided in Figure 3. The numbers in brackets on the diagram refer to the line item numbers in Table 3.


Figure 3  Schematic diagram of water inflows and outflows for the surface water store within the Daly region during the 2011–12 year. Line item numbers are provided in brackets.
Figure 3  Schematic diagram of water inflows and outflows for the surface water store within the Daly region during the 2011–12 year. Line item numbers are provided in brackets.


Allocations and diversions

Most of the diversions from surface water are to individual users under statutory rights (line item 17.6), which accounts for 60% of the total diversion (Figure 4). Approximately 32% of the diversion from surface water is for Katherine town water supply (line item 17.12).


Figure 4  Graph of diversions from surface water within the Daly region during the 2011–12 year. Line item numbers are given in brackets.
Figure 4  Graph of diversions from surface water within the Daly region during the 2011–12 year. Line item numbers are given in brackets.


The allocated diversions (line items 17.11 and 17.12) are associated with a water access entitlement. When an allocation is announced, a present obligation (water liability) is created on the surface water to deliver water to the users. As there is no carry-over provision in the region, the portion of the announced allocations that were not diverted by the end of the year was forfeited.

The entitlement, allocation announcement and forfeiture for each of these water rights during the 2011–12 year are provided in the Surface water rights section of the 'Water access and use' note.


Balancing item

The balancing item volume represents the difference between the measured opening and closing balances of the surface water store, after water inflows and outflows have been applied. This item is an indication of both the accuracy of the volumes reported and the degree to which the reported water flows represents a complete surface water store balance.

The balancing item is calculated according to Table 4.


Table 4  Balancing item for the surface water store for the 2011–12 year

Account Volume (ML)

Opening balance (30 June 2011) 500
add Total surface water inflows (see Table 3) 31,841,246
minus Total surface water outflows (see Table 3) 9,803,392
minus Closing balance (30 June 2012) 500

Balancing item—surface water
22,037,854


The calculation of the water balance on the surface water store yielded a balancing item of 22,037,854 ML. This is approximately 69% of the total surface water inflows during the 2011–12 year.

The balancing item is primarily attributed to the fact that river and floodplain losses (including evaporation and seepage) are not included in the account. It is likely that these losses are a relatively large source of surface water decrease throughout the region. In addition, the balancing item will also be attributed to uncertainty associated with the runoff (a large source of surface water increase, line item 9.4). The runoff volume is derived from a rainfall–runoff model and it is reasonable to expect a 20% uncertainty around the estimated runoff volume (+/– 6,400,000 ML).


Groundwater

Background

A description of the Daly region's surface water resources are provided in the Groundwater section of the 'Contextual information'.

Water in store

While good information exists on water movement to and from the groundwater store (see following section on 'Changes in water store'), no value is available for the volume of water in the aquifers. No value could be estimated for the volume of the groundwater asset either, indicated by dashes ('–') in Table 5. Given that the volume of groundwater within the region is unknown, the Department of Land Resource Management derive allocations for groundwater extraction based on the predicted volume of flow in the Katherine River at the end of the dry season (1 November). The predicted flow is made using models fitted for region to ensure groundwater is not over-allocated.

The Statement of Water Assets and Water Liabilities for the groundwater store is shown in Table 5.


Table 5  Statement of Water Assets and Water Liabilities for the groundwater store
Water assets Volume at 30 June 2012
(ML)
2 Groundwater  
2.1 Water table aquifer
2.2 Underlying aquifers
Total groundwater assets
   
Water liabilities  
6 Groundwater liability  
6.1 Groundwater allocation remaining 57,239
6.2 Groundwater allocation remaining – urban water system 3,940
Total groundwater liabilities 61,179
   
Opening net water assets (61,828)
Change in net water assets 649
Closing net water assets (61,179)


Changes in water store

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the groundwater store are provided in Tables 6 and 7, respectively.


Table 6  Statement of Changes in Water Assets and Water Liabilities for the groundwater store
Water asset increases 2011–12 volume
(ML)
10 Groundwater increases  
10.1 Groundwater inflow from outside region 11,000
10.2 Groundwater inflow from outside region at coast
10.3 Recharge from landscape 2,970,000
10.4 Recharge from surface water 65,000
10.6 Leakage from urban water system
Total groundwater increases 3,046,000
   
Water liability decreases  
14 Groundwater liability decreases  
14.1 Adjustment and fortfeiture of groundwater allocation 46,294
14.2 Adjustment and forfeiture of grounwater allocation – urban water system 3,291
Total groundwater liability decreases 49,585
   
Water asset decreases  
18 Groundwater decreases  
18.1 Groundwater outflow to outside region 0
18.2 Groundwater outflow to outside region at coast
18.3 Discharge to landscape
18.4 Discharge to surface water 1,219,000
18.7 Groundwater extractions – other statutory rights 4,275
18.8 Entitled extraction of non-allocated groundwater to users 1,170
Total groundwater decreases 1,224,445
   
Water liability increases  
22 Groundwater liability increases  
22.1 Groundwater allocation announcements 60,099
22.2 Groundwater allocation announcements – urban water system 4,076
Total groundwater liability increases 64,175
   
Balancing item—groundwater 1,806,316
   
Change in net water assets 649


Table 7  Statement of Water Flows for the groundwater store
Water inflows 2011–12 volume
(ML)
10 Groundwater inflows  
10.1 Groundwater inflow from outside region 11,000
10.2 Groundwater inflow from outside region at coast
10.3 Recharge from landscape 2,970,000
10.4 Recharge from surface water 65,000
10.6 Leakage from urban water system
Total groundwater inflows 3,046,000
   
Water outflows  
18 Groundwater outflows  
18.1 Groundwater outflow to outside region 0
18.2 Groundwater outflow to outside region at coast
18.3 Discharge to landscape
18.4 Discharge to surface water 1,219,000
18.7 Groundwater extractions – other statutory rights 4,275
18.8 Entitled extraction of non-allocated groundwater to users 1,170
18.11 Entitled extraction of allocated groundwater to users 14,482
18.12 Entitled extraction of allocated groundwater to urban water system 757
Total groundwater outflows 1,239,684
   
Balancing item—groundwater 1,806,316
   
Opening water storage
Add/(Less): Change in water storage 0
Closing water storage


A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Daly region is provided in Figure 5. The numbers in brackets on the diagram refer to the line item numbers in Table 7.


Figure 5  Schematic diagram of water inflows and outflows for the groundwater store within the Daly region during the 2011–12 year. Line item numbers are provided in brackets.
Figure 5  Schematic diagram of water inflows and outflows for the groundwater store within the Daly region during the 2011–12 year. Line item numbers are provided in brackets.


Allocation and extractions

Most of the extractions from the groundwater store are for licensed private use (line item 18.11), which accounts for 70% of the total extraction (Figure 6). The majority of the allocated private water extractions are for agricultural use. Approximately 4% of the extraction from aquifers is for Katherine town water supply (line item 18.12).


Figure 6  Graph of extractions from aquifers within the Daly region during the 2011–12 year. Line item numbers are given in brackets.
Figure 6  Graph of extractions from aquifers within the Daly region during the 2011–12 year. Line item numbers are given in brackets.


The allocated diversions (line items 18.11 and 18.12) are associated with a water access entitlement. When an allocation is announced, a present obligation (water liability) is created on the surface water to deliver water to the users. As there is no carry-over provision in the region, the portion of the announced allocations that were not diverted by the end of the year was forfeited.

The entitlement, allocation announcement and forfeiture for each of these water rights during the 2011–12 year are provided in the Groundwater rights section of the 'Water access and use' note.


Balancing item

The balancing item volume represents the difference between the measured opening and closing balances of the groundwater store, after water inflows and outflows have been applied. This item is an indication of both the accuracy of the volumes reported and the degree to which the reported water flows represents a complete groundwater store balance.

The balancing item is calculated according to Table 8.


Table 8  Balancing item for the groundwater store for the 2011–12 year

Account Volume (ML)

Opening balance (30 June 2011)
add Total groundwater inflows (see Table 7) 3,046,000
minus Total groundwater outflows (see Table 7) 1,239,684
minus Closing balance (30 June 2012)

Balancing item—groundwater
1,806,316


The calculation of the water balance on the groundwater store yielded a balancing item of 1,806,316 ML.

Although the volume in the groundwater stores within the Daly region could not be quantified (line items 2.1 and 2.2), the Department of Land Resource Management were able to estimate the change in groundwater store during the 2011–12 year based on groundwater model outputs. The estimated change in groundwater store of 1,827,000 ML is similar to the balancing item for the groundwater store given the uncertainty associated with each flux.

Therefore, it is considered that the volume disclosed in the balancing item (1,806,316 ML) represents the net change in groundwater store throughout the 2011–12 year.