Surface Hydrology of the Cape-to-Cape Region of Western Australia Department of Water March 2007 Surface Hydrology of the Cape-to-Cape Region Surface Water Hydrology Report No. 21 Department of Water Level 4, 168 St Georges Terrace Perth Western Australia 6000 www.water.wa.gov.au Telephone +61-8-6364 7600 Facsimile +61-8-6364 7601 For more information about this report, contact Manager, Surface Water Assessment Water Resource Management Division Department of Water March 2007 ii Department of Water Surface Water Hydrology Report No. 21 Surface Hydrology of the Cape-to-Cape Region Contents Contents ......................................................................................................................3 Summary ...................................................................................................................11 1 Introduction............................................................................................................14 2 Region Description ................................................................................................15 2.1 Background....................................................................................................................15 2.2 Gauging Stations............................................................................................................19 2.3 Landforms ......................................................................................................................23 Leeuwin-Naturaliste Ridge.....................................................................................................................23 Blackwood Plateau ................................................................................................................................23 Swan Coastal Plain................................................................................................................................23 Scott Coastal Plain ................................................................................................................................23 Darling Plateau ......................................................................................................................................25 2.4 Climate...........................................................................................................................25 2.5 Streamflow .....................................................................................................................27 Monthly flow...........................................................................................................................................28 Annual flow ............................................................................................................................................30 Flood hydrology .....................................................................................................................................32 Daily flow 35 3 Lower Blackwood River.........................................................................................38 3.1 Annual flow ....................................................................................................................38 3.2 Daily flow........................................................................................................................39 Continuous flow period ..........................................................................................................................39 Flow duration curves..............................................................................................................................41 Baseflow analysis ..................................................................................................................................42 4 Chapman Brook ....................................................................................................43 4.1 Annual flow ....................................................................................................................43 4.2 Daily flow........................................................................................................................45 Continuous flow period ..........................................................................................................................45 Flow duration curves..............................................................................................................................46 Baseflow analysis ..................................................................................................................................49 5 Margaret................................................................................................................50 5.1 Annual flow ....................................................................................................................50 5.2 Daily flow........................................................................................................................53 Continuous flow period ..........................................................................................................................53 Flow duration curves..............................................................................................................................54 Baseflow analysis ..................................................................................................................................57 6 Cowaramup...........................................................................................................58 7 Wilyabrup ..............................................................................................................59 7.1 Annual flow ....................................................................................................................59 7.2 Daily flow........................................................................................................................61 Continuous flow period ..........................................................................................................................61 Flow duration curves..............................................................................................................................62 Baseflow analysis ..................................................................................................................................63 8 Carbunup ..............................................................................................................64 8.1 Annual flow ....................................................................................................................64 Department of Water 3 Surface Hydrology of the Cape-to-Cape Region Surface Water Hydrology Report No. 21 8.2 Daily flow........................................................................................................................66 Continuous flow period ..........................................................................................................................66 Flow duration curves..............................................................................................................................67 Baseflow analysis ..................................................................................................................................68 9 Vasse ....................................................................................................................69 9.1 Annual flow ....................................................................................................................69 9.2 Daily flow........................................................................................................................72 Continuous flow period ..........................................................................................................................72 Flow duration curves..............................................................................................................................74 Baseflow analysis ..................................................................................................................................78 10 Wonnerup..............................................................................................................79 10.1 Annual flow ....................................................................................................................79 10.2 Daily flow........................................................................................................................83 Continuous flow period ..........................................................................................................................83 Flow duration curves..............................................................................................................................86 Baseflow analysis ..................................................................................................................................91 11 Capel.....................................................................................................................92 11.1 Annual flow ....................................................................................................................93 11.2 Daily flow........................................................................................................................95 Continuous flow period ..........................................................................................................................95