Drainage Operations Natural Resources South East The Bool: - PowerPoint PPT Presentation

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 Bool Lagoon Outflow Management Action at Bool Lagoon Regulator at Bool Lagoon (Regulator) – NB: indicative gauge readings at Regulator gauge board subject to draw down when regulator is in use Up to EL48.5 (flow up to Acceptable Levels < EL 48.55 AHD Levels are based on the average at the Bool Lagoon 19.8 cumecs) 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 EL 48.55 AHD * EL 48.60 m At least daily gauge readings, and recorded . discharge when *This level allows for up to 1.4 GL of storage prior to saturated (winter) and reaching EL 48.61 AHD. Based on the 2016 this is heavy Rainfall pending approximately equivalent to a single 25mm rainfall event in a saturated Mosquito Creek catchment EL 48.7m to allow for Target discharge Level EL 48.61 AHD Optimal target level, with discharge equalling the rate of balancing of flow where during ongoing saturated inflow from Mosquito Creek. (See diagram below) conditions Landholders advised 48 hours in advance, see landholder list below in Item 7. Maximum height Very EL49.52 (= Flow over the EL49.52 (remove logs if Bool Lagoon exceeds EL 49.52) EL 49.50 AHD top is 5.2 cumecs) High Level (mid winter) Or Very High Level (early EL49.52 (leave the stop logs) EL 48.58 AHD spring)

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 Inflow (GL) = 73.62 Bool Lagoon Water Balance Outflow (GL) = 53.52 Recharge (GL) = 6.13 Volume-Depth Gauge Relationship Reading NET (GL) = 19.11 Gauge Height (m AHD) = 48.52 48.51

Groundwater – Surface Water Relationship

Northern Transect Middle Transect Southern Transect

64 62 60 58 Elevation (mAHD) 56 54 52 50 48 46 0 1500 3000 4500 6000 7500 9000 10500 12000 13500 15000 Distance (m) Morphometry - LiDAR GW Levels (Oct) GW Levels (Mar)

62 61 60 59 58 Elevation (mAHD) 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 0 1500 3000 4500 6000 7500 Distance (m) Morphometry - LiDAR GW Levels (Mar) GW Levels (Oct)

Localised issues:

6000 300 5000 250 4000 200 3000 150 Discharge Volume (Ml) Lammermoor Rainfall Edenhope BoM rainfall last 60 days - Edenhope 2000 100 1000 50 0 0 1/06/2016 1/07/2016 1/08/2016 1/09/2016 1/10/2016 1/11/2016

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