Surface water management in Western Australia

Surface water management is needed wherever water erosion is a risk, where water movement control or water harvesting is required, and as part of a salinity management program.

Listed below are suitable earthwork structures, and links to detailed pages on those structures. The department recommends that any surface water management is part of a whole farm, and preferably a whole catchment, water management plan.

Surface water management options used in Western Australia

The information in this table is only a guide – seek expert advice before planning and use expert contractors for construction where necessary. Each landholder has a duty of care to make sure that flows from earthworks are not discharged indiscriminately on a neighbouring property and that stream flows are not significantly diminished or degraded.

See Conservation earthworks legal requirements of landholders for more information.

Please note, that any land degradation caused by any of these surface water management options is covered by the Soil and Land Conservation Act 1945.

Advantages of surface water management compared to subsurface drainage

treats the cause of groundwater problems, rather than the problem
cost of construction is relatively lower
surface run-off water is usually of good quality and can be stored in farm dams or directed into natural watercourses
water erosion and groundwater recharge are reduced
peak stream flow in creeks is reduced, reducing flooding, channel erosion and sedimentation
maintenance needs are low
notification of surface water earthworks is not required under the Soil and Land Conservation Act (but subsurface drainage may be).

Environmental considerations

Waterways and wetlands in catchments are important for nature conservation and local ecology as well as local drainage and floodwater discharge. Avoid disturbing the normal patterns of flow and the natural water balance of existing ecosystems.

Integration in whole-farm plans

We recommend whole-farm water management as part of a farm plan. That is, land use, management systems and infrastructure need to meet the business goals and comply with legislation. In most cases, you will need a combination of surface and subsurface water management options to achieve a sustainable system with minimal degradation.

Before constructing any earthworks, seek expert advice to avoid technical, environmental and safety risks associated with water management.

Table 1: Surface water management options.

Earthwork	Land slope (%)	Soil type	Grade (%)	Landscape position	Purpose
Absorption banks and level banks	up to 10	clay, clay loam, rocky		upper slope, below areas producing a lot of run-off	controlling run-off water where a grassed waterway cannot be safely maintained
Grade bank	up to 10	shallow duplex, loam	0.2 to 0.5	upper and mid-slope	controlling surface water erosion; harvesting water from slopes
Dams (excavated earth tanks)	up to 10	clay, shallow duplex, deep duplex, loam	up to 10	not in valley watercourse	storing and providing access to water for agricultural or household use
Roaded catchments	up to 6	clay, shallow duplex	up to 6	good clay required close to surface	improving water run-off from reduced catchment areas into dams
Grassed waterways	up to 10	most soils	up to 10	running downhill on a natural water accumulation line	providing safe disposal of overflow from dams or discharge from the end of grade banks
Seepage interceptor bank	up to 10	shallow duplex, deep duplex, sand		lower and mid-slope	controlling shallow seepage and waterlogging
Broad-based banks	2 to 6	shallow duplex, loam	0.15-0.3	upper, middle and lower slope	controlling surface water erosion; allowing easy vehicle traffic across banks
Shallow relief drains (W-drain, V-drain, spoon and spinner drains)	up to 0.2	clay, shallow duplex	up to 0.2	valley floor	removing surface water from flooded areas
Levee waterways	up to 10	clay, sand, deep duplex, shallow duplex	up to 10	valley floors and hill slopes	guiding and controlling the spread of water in drainage lines
Raised beds	0.1 to 2		0.1 to 2	valley floors and fairly level waterlogged areas	raising seed beds above the saturated soil of waterlogged areas
Evaporation basins	site specific				holding saline discharge and preventing salt discharge to environmentally sensitive areas