Drainage Operations

Natural Resources South East

The Bool: balancing flows for both ecological and flood mitigation

In a RAMSAR listed wetland

Goal 1: Manage the Drainage Network and infrastructure to retain water and flows to benefit primary production, connected groundwater systems & wetlands

Management of Bool Lagoon

Balancing flows for both ecological and flood mitigation in a RAMSAR listed wetland

Photograph by: James Davey & Ben Lively

Agreed Target Operating Levels

Big Hill Gauge Reading at Bool Lagoon

Bool Lagoon Outflow (Regulator) –

NB: indicative gauge readings at Regulator gauge board subject to draw down when regulator

is in use

Management Action at Bool Lagoon Regulator

Acceptable Levels < EL 48.55 AHD Up to EL48.5 (flow up to 19.8 cumecs)

Levels are based on the average at the Bool Lagoon Regulator, the Yards, at Big Hill, the NPWS Office and at Hacks Lagoon. However, the Big Hill gauge is an indicative average.

Optional level for discharge when saturated (winter) and heavy Rainfall pending

EL 48.55 AHD * EL 48.60 m At least daily gauge readings, and recorded .

*This level allows for up to 1.4 GL of storage prior to reaching EL 48.61 AHD. Based on the 2016 this is approximately equivalent to a single 25mm rainfall event in a saturated Mosquito Creek catchment

Target discharge Level during ongoing saturated

conditions

EL 48.61 AHD EL 48.7m to allow for balancing of flow where

Optimal target level, with discharge equalling the rate of inflow from Mosquito Creek. (See diagram below)

Landholders advised 48 hours in advance, see landholder list below in Item 7.

Maximum height Very High Level (mid winter)

EL 49.50 AHD EL49.52 (= Flow over the top is 5.2 cumecs)

EL49.52 (remove logs if Bool Lagoon exceeds EL 49.52)

Or Very High Level (early spring)

EL 48.58 AHD EL49.52 (leave the stop logs)

Aerial View 23/09/2016

Statutory Plan of SEWCD Board

• South Eastern Water Conservation and Drainage Act 1992

• SEWCD Board Management Plan to 2018/19- Goal 1: Manage the Drainage Network and infrastructure to

retain water and flows to benefit primary production, connected groundwater systems & wetlands

• Bool Lagoon Game Reserve and Hacks Lagoon Conservation Park, Park Management and Ramsar Plan (Park Management Plan, 2006).

• Guidelines for the Operation of Bool Lagoon and Drain M Regulators for Flood Mitigation Purposes (J.E. Nitschke, 1984)

Operating Challenges

Groundwater

• Hacks and Bool Lagoon very complex site

• Known as a Boinka – wetland generated through the occurrence of a major groundwater discharge zone over a long period

• Studies have shown that there are periods where groundwater will discharge into Bool Lagoon and other periods where surface water is recharging to groundwater.

•Landholders concerned of the effect surface water levels within Bool Lagoon is having on the water table in surrounding agricultural land during wet years

Oct 2016 RSWL (mAHD)

Groundwater- surface water dynamics• Water balance for 2016 wet season

Precipitation (GL) = Evaporation (GL) = Evapotranspiration (GL) =

17.15 11.16 3.49

Bool Lagoon Water BalanceInflow (GL) = 73.62 Outflow (GL) = 53.52

Recharge (GL) =

6.13

NET (GL) = 19.11Gauge

Reading

Volume-Depth Relationship

Gauge Height (m AHD) = 48.52 48.51

Groundwater – Surface Water Relationship

Southern Transect

Middle Transect

Northern Transect

46

48

50

52

54

56

58

60

62

64

0 1500 3000 4500 6000 7500 9000 10500 12000 13500 15000

Elev

atio

n (

mA

HD

)

Distance (m)

Morphometry - LiDAR GW Levels (Oct) GW Levels (Mar)

43

45

47

49

51

53

55

57

59

61

44

46

48

50

52

54

56

58

60

62

0 1500 3000 4500 6000 7500

Elev

atio

n (

mA

HD

)

Distance (m)

Morphometry - LiDAR GW Levels (Mar) GW Levels (Oct)

Localised issues:

0

50

100

150

200

250

300

0

1000

2000

3000

4000

5000

6000

1/06/2016 1/07/2016 1/08/2016 1/09/2016 1/10/2016 1/11/2016

Discharge Volume (Ml)

Lammermoor Rainfall

Edenhope BoM rainfall

last 60 days - Edenhope

Proposed Next Steps:

Installation of more piezometers to evaluate extent of groundwater mound and relationship with surface water levels in Bool Lagoon

Installation of monitoring stations at proposed sites within Mosquito Creek catchment

Review of “Guidelines for the Operation of Bool Lagoon and Drain M Regulators for Flood Mitigation Purposes” developed in 1984 to check still relevant with current catchment and new information

Produce new operation guidelines for Bool Lagoon

Publish 2017 Bool Lagoon Technical Report

Development of water balance model for predictive/scenario tool