Regulation index

Find further information on the Conservation of Freshwater Ecosystem Values (CFEV) Program and its data at www.dpipwe.tas.gov.au/cfev.

Attribute data

TitleRegulation index

CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment

CreatorGIS Unit, Information and Land Services Division, Department of Primary Industries and Water (DPIW)

DescriptionThe amount of regulation of the natural flow regime due to the effect of all water storage upstream

Input data

  1. CFEV Mean Annual Run-off (natural) attribute data
  2. CFEV River Section Catchments (RSC) spatial data
  3. CFEV Waterbody artificiality attribute data
  4. CFEV Waterbodies (invalid) spatial data
  5. Hydro infrastructure and discharge data (volume), Hydro Tasmania
  6. Land Information System Tasmania (LIST) Farm dam layer, DPIW
  7. Water Information Management System (WIMS) database, DPIW

Lineage

The flow regulation index, REGI, rates all river sections according to the amount of regulation of the natural flow regime due to the effect of all water storage upstream. This assumes that one dam volume is captured per year. This is comparable to the active Hydro storage volume. The regulation index is derived by summing all known storage volumes upstream and dividing the sum by the modelled natural MAR for the river section in question:

The sum of all ‘active’ storage within the upstream RSCs catchment and the local RSC is divided by the accumulated natural MAR of RSCs (RSC_AMARNT). The accumulated natural MAR was modelled for all river sections and RSCs. Cumulative storage was calculated by summing all ‘active’ storage volumes for all ‘modified’ waterbodies upstream in the catchment. These include:

  1. CFEV waterbodies with an artificiality score (WB_ARTIF) = 0
  2. all LIST-mapped large and small farm and other storage dams, with volumes estimated from an area-volume relationship (the ‘invalid’ waterbodies)
  3. all dams not mapped but included in the WIMS database.
  4. all ‘active’ Hydro storage (i.e. useable volumes supplied by Hydro Tasmania).

The cumulative upstream storage was calculated using the following rules:

  1. Create the ‘modified’ waterbodies data set:
    1. Draft data set: Combine the following data sets to develop a single ‘modified’ waterbodies data set (note, there may be overlap between the following criteria):
      1. all ‘invalid’ waterbodies
      2. all ‘valid’ waterbodies that have been rated as being artificial (WB_ARTIF = 0) (see Appendices 0 and 0)
      3. all WIMS dams (catchment dams, off-stream dams, and on-stream dams)
      4. all farm dams on LIST identified as not being included in WIMS (approximately 31% of all farm dams identified from LIST)
    2. Final layer: Identify and remove duplicates of WIMS dams:

      3. Remove WIMS dam if a WIMS Point falls within 200 m of another artificial waterbody of similar volume (within range of 4 times the capacity);

      Note:

      1. Arthurs Lake was removed from WIMS data set
      2. Lake Leake storage volume was derived as being = 20% of storage capacity
      3. those WIMS dams with 0 (null) capacity value in the WIMS database were set a nominal capacity = median value of range of all WIMS total capacity records.
  2. Calculate storage volume (ML) for all ‘modified’ waterbodies (as described above):
    1. For Hydro storages, assign with the useable volume (USE_VOLUME) supplied by Hydro Tasmania
    2. For WIMS dams, assign with the capacity (CAPACITY from WIMS database) (ML)
    3. For all other waterbodies (non Hydro and non WIMS) (i.e. farm dams not in WIMS and other storages (e.g. mine tailings ponds, Lake Leake and Tooms Lake etc.)), calculate their volumes from their polygon areas using the equation:

Volume (ML)=21.129*(Area(ha)1.1057)

This equation was developed by analysis of relationships between farm dam volume and surface area, using the WIMS data for off-stream and catchment dams (n = 167, after reviewing and screening the data for unreliable and bad records). The relationship compared favourably against a similar relationship developed by Sinclair Knight Merz (SKM 2003; Lowe et al. 2005).

  1. Assign ‘modified’ waterbodies to the RSCs.
  2. Calculate the sum of all storage volume per RSC.
  3. Calculate the upstream cumulative storage by summing all the storage volumes in all upstream RSCs plus the local RSC.
    1. Divide the sum of upstream cumulative storage (value from rule 5) by the natural MAR (RSC_AMARNT). Assign value to each RSC.

The regulation index has no units and ranges from zero, where there are no storages upstream, to a large positive number. Banding ranges for the regulation index were assessed following inspection of index values from a range of river sections and comparing with in-stream impacts observed by Davies et al. (1999) from selected Hydro-impacted streams. Impacts on stream biotic condition and geomorphology were considered to be high (low condition) when the regulation index is >0.15, medium when between 0.05 and 0.15, and low to absent when <0.05.

The specific rules for calculating the regulation index for karst, rivers, waterbodies and wetlands are outlined below.

Data limitations

The regulation index inherits all the data limitations of the derivation processes and input data.

Date createdOctober 2004

Scale and coverage1:25 000; Statewide

References

Davies, P.E., Cook, L.S.J. and McKenny, C.E.A. (1999). The influence of changes in flow regime on aquatic biota and habitat downstream of the Hydro-electric dams and power station in Tasmania. Hydro Technical Report Project No. 95/034. Hobart, 128 pp.

Lowe, L., Nathan, R., and Morden, R. (2005). Assessing the impact of farm dams on stream flows, Part II: Regional characterisation. Australian Journal of Water Resources 9: 13-26.

SKM. (2003). Estimating available water in catchment using sustainable diversion limits. Farm dam surface area and volume relationship. Report to the Department of Sustainability and Environment. Draft B. Sinclair Knight Merz, Melbourne.

Column headingKT_REGI, RS_REGI, WB_REGI

Type of dataContinuous but also exists in a categorical format (see Table 1).

Number of classesKT_REGI_C = 3, RS_REGI_C = 3, WB_REGI_C = 3

Assigning values to ecosystem spatial units

A regulation index was assigned to karst, river and waterbody spatial units using the following rules.

Karst (KT_REGI)

  1. Divide RSCs assigned to each karst unit into two subsets: ‘big river catchments’ (those RSCs with an accumulated current MAR (RSC_AMARNM)>48.2 GL) and ‘small river catchments’ (all other RSCs). Note, more details on the rational for the big and small catchment split are provided in the MAR section.
  2. Calculate the regulation index for ‘big river catchments’ by a MAR weighted average of all downstream-most catchments in the big river catchment group for each karst area as:

    3. Where:

    Big river regulation index = Regulation index for the karst spatial unit (only taking into account the RSCs of the karst local catchment which have RSC_AMARNM>42.8 GL)

    RSC_REGI (1…n) = Regulation index for the RSCs of the karst local catchment which have RSC_AMARNM>42.8 GL

    RSC_MAR (1…n) = Current MAR value for the RSCs of the karst local catchment which have RSC_AMARNM>42.8 GL

    RSC_ACNMAR = Upstream accumulated current MAR value for the RSCs of the karst local catchment which have RSC_AMARNM>42.8 GL

  3. Calculate the regulation index for ‘small river catchments’ by a MAR weighted average of all downstream-most catchments in the small river catchment group for each karst area as:

    4. Where:

    Small river regulation index = Regulation index for the karst spatial unit (only taking into account the RSCs of the karst local catchment which have RSC_AMARNM≤42.8 GL)

    RSC_REGI (1…n) = Regulation index for the RSCs of the karst local catchment which have RSC_AMARNM≤42.8 GL

    RSC_MAR (1…n) = Current MAR value for the RSCs of the karst local catchment which have RSC_AMARNM≤42.8 GL

    RSC_ACNMAR = Upstream accumulated current MAR value for the RSCs of the karst local catchment which have RSC_AMARNM≤42.8 GL

  4. Assign all karst spatial units with an regulation index as a weighted average of the big and small regulation values as follows:
    1. Karst spatial units associated with both big and small catchments:

      2. KT_REGI = (Big river regulation index * 0.2) + (Small river regulation index * 0.8)

      Where:

      KT_REGI = Regulation index of the karst spatial unit

      Big river regulation index = Regulation index for the karst spatial unit (only taking into account the RSCs of the karst local catchment which have RSC_AMARNM>42.8 GL) (calculated in Step 2)

      Small river regulation index = Regulation index for the karst spatial unit (only taking into account the RSCs of the karst local catchment which have RSC_AMARNM≤42.8 GL) (calculated in Step 3)

River sections (RS_REGI)

Assign the regulation index of the RSC (as calculated above) directly to the river section it is associated with.

Waterbodies (WB_REGI)

Assign the regulation index of the RSC (as calculated above) directly to the waterbody it is associated with.

Each of the karst, river and waterbody spatial data layers has the continuous regulation index data categorised according to Table 1. The categorical data was used for reporting and mapping purposes.

Table 1. Regulation index categories for karst, rivers and waterbodies.

Category

Karst

(Min to max values)

Rivers

(Min to max values)

Waterbodies

(Min to max values)

1

0 to <0.05

0 to <0.05

0.15 to 153.4145

2

0.05 to <0.15

0.05 to <0.15

0.05 to <0.15

3

0.15 to 0.778101616

0.15 to 1581154893

0 to <0.05

CFEV assessment framework hierarchy

  1. Karst>Statewide audit>Condition assessment>Naturalness score (KT_NSCORE)>Hydrology (KT_HYDRO)
  2. Rivers>Statewide audit>Condition assessment>Naturalness score (RS_NSCORE)>Geomorphic condition (RS_GEOM)>Flow change (RS_FLOW)
  3. Rivers>Statewide audit>Condition assessment>Naturalness score (RS_NSCORE)>Geomorphic condition (RS_GEOM)>Sediment capture-surrogate (RS_SEDCA)
  4. Waterbodies>Statewide audit>Condition assessment>Naturalness score (WB_NSCORE)>Hydrology (WB_HYDRO)