Supplementary Access Gwydir Valley 2008

Craig Cahill

Access To Date

• Three separate supplementary events since the embargo was lifted in December 2007.

• Gwydir river starting 6th January 2008.• Carole creek starting 22nd January 2008.• Complete system starting 5th February 2008

(This includes Gil Gil creek).

Gwydir River January 2008

• Localised rain event U/S of Gravesend.• Available flow to be shared 2607ML.• 8% announcement made from Boolooroo Weir

to Caithness on the Lower Gwydir.• 1255ML announced 1021ML pumped.

Carole Creek January 2008

• Localised rain event and inflow from Marshall ponds.

• Available flow to be shared 2100ML.• 3% announcement made from Midkin to

Cleveland.• 920ML announced 918ML pumped.

Complete System Announcement

• General falls across whole valley with isolated heavy rainfall.

• Total Flow Volume

Gravesend inflow 60,187ML

Gil Gil Creek inflow 18,077ML

Marshall Ponds inflow 6,353ML

Mehi River inflow 6,175ML

Total Flow 90,792ML

Complete System Announcement

• Available flow to be shared

Total Flow Volume 90,792ML

3T Rule 6,000ML

D/S Orders 1,764ML

Available flow to be shared 83,028ML

50% Consumptive share 41,514ML

Total Supplementary extracted 40,301ML

Over Pumping debited to other accounts

1,392ML

Total Pumping 41,693ML

Complete System Announcement’s

Gwydir RiverCopeton to Boolooroo Weir

25%

Boollooroo Weir to Wandoona 15%

Mehi RiverTareelaroi Weir to Combadello Weir

25%

Combadello Weir to Myambla 15%

Moomin CreekCombadello Weir to Alma Bridge

15%

Downstream Alma Bridge 17%

Complete System Announcement’s

Carole CreekBoolooroo Weir to Midkin South

23%

Midkin to Windmill 27%

Brigalows to Dodds 29%

Bullamon to Medgun 48%

Gil Gil CreekByra to Cleveland

100%

Determining Section Announcements

• Forecast volume of event and shape of hydrograph.

• Assess if there is surplus to requirements.• Determine what section is next on the three

year rolling average, while considering deliverability, event volume, shape of hydrograph and past announcements.

Principals of Three year Rolling Average

• Announcements are made based on opportunity to access supplementary flows.

• To share opportunity across all section as equitable as possible, based only on when flows are available.

Summary of Announcements made from 30th June 2005 to 5th Feb 2008

Gwydir Valley Supplementary Access Granted Expressed as a Percentage of Supplementary Access Limit

0

50

100

150

200

250

300

350

0 10 20 30 40Water Users (Stream Order)

Cu

mu

lati

ve A

nn

ou

ncem

en

ts (

%)

MEHI MOOMI N CAROLE GWYDI R

Summary of Announcements made from 30th June 2005 to 17th March 2008

Gwydir Valley Supplementary Access Granted Expressed as a Percentage of Supplementary Access Limit

0

50

100

150

200

250

300

350

400

450

500

0 10 20 30 40Water Users (Stream Order)

Cu

mu

lati

ve A

nn

ou

ncem

en

ts (

%) MEHI MOOMI N CAROLE GWYDI R