Bore vs Farm Dam: Choosing Your Property’s Water Supply

Start with the water you need at the trough, garden, shed or irrigation outlet. Ask how much must arrive on the busiest summer day, what quality that use requires, and how long the property must keep operating when its usual supply stops. Use those answers to write the brief for both options.

A useful comparison puts the same demand, service standard and contingency allowance in front of the dam contractor and bore specialist. Do not compare a fully installed dam-and-pump proposal with a drilling-only estimate. Ask each supplier to identify what remains untested, unpriced or subject to approval before treating either proposal as a complete water supply.

Bore vs farm dam: what evidence should you compare?

Groundwater is water held below ground in soil and rock; an aquifer is a geological formation that stores and transmits it. A bore accesses that underground source, while a farm dam stores water at the surface, including runoff from its catchment. A catchment is the area draining towards a particular storage or outlet.

Treat the following table as a request for evidence, rather than a verdict that one source always wins. Write “not yet established” against unanswered questions. Then price the investigations needed to replace those unknowns with information you can use.

Decision	Ask about the bore	Ask about the dam
Available supply	Request pumping-test results and an assessed operating rate.	Request a catchment assessment and usable storage estimate.
Water quality	Request laboratory results for the proposed use.	Assess incoming water and stored-water quality risks.
Dry-period performance	Check seasonal groundwater records and extraction conditions.	Test a period without useful runoff in the water budget.
Delivery	Include pumping, power, tanks and distribution.	Include intake, pumping or gravity delivery and distribution.
Site evidence	Review local bore records and drilling uncertainty.	Investigate soil, levels, access and construction constraints.
Complete cost	Include testing, unsuccessful drilling risk and maintenance.	Include investigations, earthworks, approvals and maintenance.

For the dam side, start with our farm dam construction planning guide. Keep the comparison focused on your property rather than copying the size or equipment used next door. Ask for the assumptions behind each recommendation, especially any assumption about water arriving during a dry period.

What proves a groundwater supply is suitable?

Bore yield is the rate at which a bore supplies water under stated conditions, usually expressed in litres per second or litres per hour. Request the test method, duration, water levels and interpretation alongside any quoted yield. Do not let a single flow number stand in for an assessment of the operating rate appropriate to your proposed use.

WaterNSW recommends a constant-rate pumping test lasting at least six hours after completion of a domestic and stock bore; its guidance distinguishes longer testing for relevant commercial bores and notes separate inland requirements (WaterNSW bore testing and approvals guidance).

Drawdown is the reduction in groundwater level caused by pumping. Ask the driller or groundwater specialist to explain what the measured drawdown and subsequent recovery mean for pump placement and proposed operation. Request written advice about the limits of the test rather than interpreting a short pumping demonstration yourself.

Pair that assessment with water-quality testing for the intended use. Tell the adviser whether the water is for cattle, household use, garden irrigation or a commercial crop. Request a clear statement of any treatment requirement and include that equipment in the proposal. Do not accept appearance, taste or a neighbour’s experience as the only evidence that the water suits your use.

The NSW Local Land Services water-sources example describes a bore about 40 metres deep, a standing water level about 12 metres below ground and delivery of about 14,000 litres per day; those figures describe that property, not an expected result from a new bore elsewhere (NSW farm water-source guidance).

How should you assess farm water storage?

A water budget is a comparison of water entering storage, water used and water lost over a chosen period. Build yours around a dry-season scenario as well as an average year. Ask the designer to show when the dam refills, what happens if that refill is missed and which demand must be protected first.

Separate the excavation’s total capacity from the volume you plan to use. Identify the lowest workable intake level and any reserve you intend to retain. Our guide to sizing a farm dam provides the next planning discussion, but request site-specific measurements before committing to an earthworks quantity.

Include evaporation, seepage and distribution leaks as explicit budget items. Evaporation is water leaving the surface as vapour; seepage is water moving through the storage’s bed, banks or surrounding ground. Ask the designer which loss assumptions are measured, which are estimated and how sensitive the proposed storage is to those estimates.

For a bore-backed system, Agriculture Victoria’s rainfed dairy planning guide recommends about three to five days of tank storage to cover pump breakdowns; treat that as a planning reference, not a guarantee that the same reserve suits every property (Agriculture Victoria farm-water planning guide, page 15).

Apply the same practical question to a dam: how will water reach the stock if the usual delivery equipment fails? Include access for repairs, an alternative supply connection and a nominated person to check levels. Put those arrangements alongside the farm dam maintenance checklist, rather than leaving them until an outage.

Compare water supply costs and approval conditions

Request separate prices for investigation, construction, delivery equipment and ongoing operation. For the bore, ask what happens commercially if the first hole does not produce suitable water. For the dam, ask which soil and site conditions are assumed in the price and how unsuitable material or additional work would be handled.

Lindsey Hughson’s Big Ditch records for a completed dam at Lorne, NSW, in 2019 record 76.5 excavator hours. That is a documented construction job, not a standard allowance for another dam or evidence of what a competing bore would have cost.

Use that distinction when reviewing a quote. Ask for the proposed work and its assumptions, not a promise that your property will match somebody else’s hours. Request a clear boundary between the dam works, specialist investigations and the equipment needed to deliver water after construction.

For either option, ask for the expected pumping duty, power arrangement, maintenance responsibilities and replacement items. Pumping duty is the combination of flow and pressure the pump must deliver. Compare proposals at the same duty and ask the supplier to explain the energy estimate, including the assumed operating hours and electricity or fuel price.

Before drilling or earthworks, ask the relevant water authority to confirm the approvals for both construction and intended water use. In NSW, check the WaterNSW guidance cited above rather than assuming a domestic and stock purpose removes the need for a bore works approval. Ask separately about irrigation, commercial use, extraction conditions and any proposal to transfer water between storages.

Outside NSW, obtain the equivalent advice for your state and water source. Also request confirmation of council planning, vegetation and heritage requirements where relevant to the site. Put the written advice and approval conditions into the project brief; do not treat a contractor’s availability as permission to start.

When should you consider both sources?

Consider a combined proposal when you can identify a specific job for each source. You might ask the designer to investigate a bore for routine supply and a dam for a separate storage reserve. Test the proposal against an actual failure scenario rather than counting two water sources and assuming the property has adequate backup.

Reticulation is the network of pipes and fittings distributing water around the property. Review the shared parts of that network: ask what happens if the main pipe breaks, the header tank empties or the power supply stops. A header tank is an elevated storage used to supply downstream outlets, often by gravity. Have the designer show which outlets remain supplied under each scenario.

1. Measure current demand and identify the busiest delivery period.
2. List the required water quality for each intended use.
3. Obtain bore evidence and assess the proposed dam site.
4. Confirm construction permissions and intended water-use conditions.
5. Price complete systems against the same demand and backup brief.
6. Choose the option whose remaining risks you can manage.

Bring the property plan, existing water records and proposed uses when you discuss the dam option with Big Ditch. Keep bore drilling and groundwater interpretation with the appropriate specialists. Ask all parties to work from the same demand figures so the final comparison answers one question consistently.

Frequently asked questions

Is a bore more reliable than a dam?

Do not assume it is: compare the evidence for the particular property. Request the bore’s tested operating conditions and water-quality results, then compare them with the dam’s inflow assumptions and usable storage budget. Include the equipment delivering water from either source. Ask what supply remains available during a dry period, pump failure or power outage before deciding which proposal offers the better practical reserve.

Can bore water be stored in a farm dam?

Treat that as a separate design and approval question, not an automatic next step. Ask the water authority whether the proposed extraction, transfer and use are permitted, and ask the designer to compare open storage with a tank. Include water quality, storage losses and delivery arrangements in that comparison. Do not price a combined system on the assumption that every available water source can be used interchangeably.

Should a small property choose a bore first?

Choose the investigation first, rather than committing to the bore or dam immediately. Write down the intended uses, peak demand, available space and required reserve, then obtain advice on both the groundwater and dam-site prospects. Ask for investigation costs separately from construction. This lets you decide what evidence is worth buying before accepting a complete supply proposal, rather than using property size alone as the deciding factor.

Weighing up a bore vs farm dam? Book a site inspection with Big Ditch and assess the dam option against your property’s water needs.