Catchment Management Plan - Hunter Water

2.4 The WilliamsRiver CatchmentCatchmentareaAnnualrainfallAreassuppliedLand use breakdownof catchmentPopulation growth forecast2010-2030974km 21152mm(at Dungog)Water pumpedinto GrahamstownDam at SeahamWeir80% farming and rural, 14%National Park or State Forest,6% Hunter Water freeholdCurrent population 5 2,350 residents. The mainpopulation growth will be in uptake of ruralresidential land – by 2030 the towns of Dungogand Clarencetown may have an additional 250and 450 of these lots, effectively doubling thepopulation of Clarencetown. A modest increasein urban centre populations only.Northern reachesThe Williams River has its headwatersemanating from forested and pastoralland approximately 140 kilometresnorth of Newcastle (Figure 8). Theheadwaters of the Williams drain thesouthern Barrington Tops National Parkand pastoral hinterland. To the east,the Chichester River also begins in theBarringtons and joins the Williams atBandon Grove. Land use in the northernreaches is a mixture of National Park,forestry and extensive cattle farmingwith some irrigated pasture cropping onthe river flats.The Williams continues in a southerlydirection through the major townshipsof Dungog (population 2,100) andClarence Town (population 1,000). Thecatchment of this portion of the riveris again primarily pastoral, but withpockets of more intensive agriculture(eg poultry and dairy farms) andurban development. There is a sewagetreatment plant at Dungog that irrigateseffluent onto a dairy farm adjacent tothe river and a treatment plant underconstruction at Clarence Town.Southern reachesAt Mill Dam Falls (approximately 45kilometres from Newcastle) the Williamschanges from a free flowing river into amodified river weir pool, Seaham Weirpool. The pool is approximately 18kilometres in length and is effectively freefrom tidal influence due to the completionof Seaham Weir in 1978. This body ofwater has a longer retention time thanthe river above this point and thus maybehave similarly to a long reservoir inperiods of low river flow. Figure 7 is ofSeaham Weir looking south.On average the weir pool is betweenfive and eight metres deep and must bemaintained at a specific level to reduceerosion of the river bank and preventflooding of the surrounding property.Despite these rules, erosion of theriverbank is a significant issue on the weirpool. The worst erosion occurs wherebanks have largely been cleared for thesurrounding cattle pasture and waterskiing boats are permitted. The banks ofthe pool are unfenced in parts, adding toerosion problems and allowing cattle toenter the water.After rainfall and under higher flows,water is transferred through BalickeraCanal to Grahamstown Dam using pumpsat Balickera Pump Station (Figure 9).During dry times the majority of flow inthe Williams is sourced from the uppercatchments and during wet times thelower catchment dominates. Water qualityrisk assessments for this source indicatedthat nutrients, turbidity, pesticides,organics and algal toxins were theprincipal issues for this system.Figure 7: Seaham Weir looking south5 Estimate based on Australian Bureau of Statistics 2006 Census dataCATCHMENT MANAGEMENT PLAN . ssS . 001 . JUNE201013