Daly: Supporting information
- Poor wet season rainfall contributed to low runoff and aquifer recharge across the region.
- The dry conditions resulted in an annual drop in aquifer storage for the third consecutive year.
- 34% of the allocated water was taken in 2019–20, mainly for agricultural purposes.
For further information on the regions water accounting statements scroll down this page or click on the links below:
Water assets
Groundwater assets
- Volumes of water stored in the aquifers cannot be quantified due to a lack of available data; however, information on the total annual change in aquifer storage is available.
Figure S1 Total annual change in aquifer volume in the region at 30
June 2020 compared with the previous 8 years
- Below-average wet season rainfall contributed to low groundwater recharge and an annual decrease in aquifer storage of 491 GL.
- There have been seven annual drops in storage over the last nine years, reflecting a sustained period of relatively poor wet season rainfall in the region.
- The very large increase in storage in 2011–12 was primarily attributed to well above-average rainfall over a 2-year period associated with the 2010–12 La Niña event.
Surface water assets
- The volume of surface water in the region at 30 June 2020 was 4 GL, all of which is water held in rivers. This volume changes little from year to year.
- The volume of water in the region's storages (see Region description) could not be quantified; however, this volume is very small compared with the volume of water in rivers.
Water liabilities
- Water liabilities in the Daly region refer to the volume of allocation remaining on licence entitlements at the end of the 2019–20 year.
| Description | Individual users (ML) | Urban system (ML) | |
| Opening balance at 1 July 2019 | 0 | 0 | |
| add | Allocation | 6,013 | 3,417 |
| less | Allocated diversion | 844 | 2,877 |
| less | Adjustment and forfeiture | 5,169 | 540 |
| Closing balance at 30 June 2020 | 0 | 0 | |
| Description | Individual users (ML) | Urban system (ML) | |
| Opening balance at 1 July 2019 | 0 | 0 | |
| add | Allocation | 142,307 | 4,356 |
| less | Allocated diversion | 48,232 | 398 |
| less | Adjustment and forfeiture | 94,075 | 3,958 |
| Closing balance at 30 June 2020 | 0 | 0 | |
- As there are no carry-over provisions for water supply licences in the Daly region, the portion of water allocation that has not been abstracted at the end of a water year is forfeited and the allocation remaining at the end of the year was 0 ML.
- A more detailed description of water allocations in the Daly region is given in the Water use section below.
Water flows
Figure S2 Water inflows and outflows for the surface water store during the 2019–20 year
Figure S3 Water inflows and outflows for the groundwater store during the 2019–20 year
- Total water flows into the region's storages was 2,558 GL. The key item contributing to water inflows was runoff, which made up 70% of the total water inflows for the region.
- For the second consecutive year, runoff was much lower than average (based on modelled data from 1971–2020) due to relatively poor wet season rainfall across the region.
- The key item contributing to water outflows for the region was river outflow, which made up almost three quarters of the total outflows. River outflow was well below average due to the relatively dry conditions and low runoff across the region.
- Water taken for consumptive use was 62 GL, around 2% of the total outflow (see Water use section below).
Water use
Figure S4 Surface water taken during the 2019–20 year in the
region's key water management areas
Figure S5 Groundwater taken during the 2019–20 year in the
region's key water management areas
- Total surface water diverted in the region was 9,090 ML, mostly from the Katherine River.
- 59% of the surface water diversions were made under statutory rights; 32% were for the urban system and 9% were supplied to licenced individual users.
- Total groundwater extracted in the region was 53,090 ML, mostly from the Oolloo Dolostone and the Tindall Limestone water allocation plan areas.
- 91% of the groundwater extractions were supplied to licenced individual users; 1% were for the urban system and 8% was made under statutory rights.
Figure S6 Surface water allocations and diversions in the Daly
region for the years ending 30 June, from 2012–2020
- In 2019–20, total surface water allocation was 9 GL, mostly from the Katherine River for town supply. 40% of the allocated surface water was taken.
- Surface water diversions to the urban system were higher than previous years. This increase was likely to be influenced by the very dry conditions across the region resulting in a high demand from customers.
- Surface water allocations for the urban system returned to pre-2018 volumes. In 2018–19, allocations were increased as a precautionary measure in case groundwater supply to Katherine was further limited by the presence of per- and poly-fluoroalkyl substances (PFAS) and more surface water was needed to meet the town's water supply requirements.
- Surface water allocations and diversions for individual users were similar to the last few years. The relatively large increase in surface water allocation in 2014–15 was due to a number of new licences being granted for the Katherine River, primarily for agricultural purposes.
- The estimated volume of water diverted under other statutory rights remained unchanged
Figure S7 Groundwater allocations and extractions in the Daly
region for the years ending 30 June, from 2012–2020
- In 2019–20, total groundwater allocation was 147 GL, mostly from the Oolloo Dolostone and Tindall Limestone aquifers for agricultural purposes. 33% of the allocated groundwater was taken.
- Groundwater extractions for individual users were higher than the previous few years. This increase was likely to be influenced by the very dry conditions across the region resulting in a high demand from customers.
- Groundwater extractions for the urban system remained relatively low, similar to last year. Groundwater supply to the town of Katherine has been limited during the last three years due to a requirement for groundwater to be filtered to remove per- and poly-fluoroalkyl substances (PFAS) before transfer to the urban system (see Water restrictions for more detail).
- The estimated volume of water extracted under other statutory rights remained unchanged.
Water restrictions
- A per- and poly-fluoroalkyl substances (PFAS) treatment plant commenced operation in the region in October 2017 to remove higher levels of PFAS identified in the town of Katherine's groundwater supply. Groundwater extracted from the Tindall Limestone Aquifer was filtered to remove PFAS prior to transfer to the urban system.
- The PFAS removal process has meant that groundwater supply to the town of Katherine has been limited during the last three years. Although most of the town water supply for Katherine comes from surface water, the drop in groundwater contribution meant total water usage in Katherine needed to reduce by 20% to ensure a sustainable water supply.
- A 3-day a week sprinkler roster for properties in Katherine remained in place during 2019–20. For more information, refer to the Northern Territory Power and Water's Living Water Smart Katherine website.
Cultural and environmental water
Cultural benefit
- The water allocation plans for the Daly region recognise Aboriginal rights and interests in water and provide for Aboriginal interests through measures to limit extraction of groundwater (see the Cultural water management section in the 'Region description').
- The cultural water provisions are strongly linked to the environmental water requirements in the plans (see Environmental benefit below).
Environmental benefit
Environmental water provisions
- Environmental water provisions have been established for the Tindall Limestone Aquifer based on a minimum flow requirement in the Katherine River.
Figure S8 Environmental water provisions for the Tindall
Limestone Aquifer
- Water provisions are defined based on a model-predicted flow rate at the end of the dry season on 1 November along the Katherine River.
- The flow on 1 November is equated to an annual groundwater discharge volume from the Tindall Limestone Aquifer into the river. The proportion of discharge reserved for environmental benefit is based on this volume. The remainder of the annual groundwater discharge is allocated for extraction for consumptive use.
- A more detailed description of the environmental water provisions for the Tindall Limestone Aquifer is provided in the Katherine Tindall Limestone Aquifer Water Allocation Plan.
- It should be noted that the above provisions have been revised in the updated version of the plan released in August 2019 and these will apply from 2020–21 onwards.
Environmental water outcomes
Figure S9 Environmental water outcomes for the 2019–20 year
- The environmental water provisions for the 2019–20 year for the Tindall Limestone Aquifer were based on a normal-to-wet year classification and a predicted annual groundwater discharge of around 106,000 ML.
- Based on the observed flow on 1 November 2019, groundwater discharge from the aquifer into the river was approximately 45,000 ML, lower than predicted.
- 14,833 ML was actually taken from the Tindall Limestone Aquifer for consumptive use (see Water use section above), which means that just under 70% of the year's groundwater discharge was for environmental benefit.