Are there benefits to investing in reservoirs?
Implications of installing rubber liners in reservoir builds
Investing in the build of reservoirs has the potential to offer improved water security. Rainwater harvesting reservoirs store water during wet periods for use in dry months, reducing pressure on rivers and aquifers. This can be highly valuable for farmers in particular, but by how much depends on several local and operational factors such as climate, soil, crops, topography, and capital.
Key benefits of investing in building reservoirs
- Farmers rely on consistent water supplies for irrigation, especially during prolonged dry spells. Water is vital for food security.
- They offer protection of natural ecosystems. By storing water for human use, reservoirs reduce over-abstraction from rivers and wetlands, helping to protect biodiversity and aquatic habitats.
- Depending on design and location, they can be used as a form of flood control. Certain multi-use designs can buffer heavy rainfall, reducing downstream flood risk.
While there are very clear positive factors to increasing water storage solutions in the UK, this needs to weighed up against negative environmental impacts. New reservoirs can flood habitats, displace wildlife, and disrupt local ecosystems during construction. They must therefore be sited carefully with environmental mitigation plans.
The next financial investment is to decide whether a new reservoir build should be lined or not. Most modern farm reservoirs are, and rubber (or synthetic polymer) liners are among the most common methods to prevent seepage. The exact liner choice depends on soil type, reservoir size, and budget. Here is a break down of a lined versus unlined reservoir which we hope will help with calculating the cost of investing in a reservoir.
Comparison: Lined vs Unlined Reservoirs
| Aspect |
Unlined Reservoir |
Lined Reservoir |
| Seepage / Water Loss |
Higher losses. Depending on soil permeability, water table, etc., losses can be large (20-50% or more in some cases).
For example, in unlined irrigation canals seepage can be 19-30% of water diverted. |
Much lower losses. Lining reduces seepage dramatically: some studies show <10% seepage in lined canals compared to ~20-30%+ in unlined. (Exact loss depends on liner type, installation quality, and presence of defects/cracks). |
| Efficiency & Water Use |
Lower usable volume per unit rainfall/runoff due to seepage; more of the stored water is lost to ground. Water use efficiency is correspondingly lower. |
Higher usable storage; more water stays in the reservoir. Better reliability for irrigation/stock during dry periods. Efficiency gains particularly important where water is scarce or costly. |
| Initial Cost |
Cheaper upfront. You avoid the cost of synthetic liners or heavy clay sealing and associated more precise construction. |
More expensive initially. Costs include liner material, labour to shape/prepare site, ensuring slope/smooth surfaces, protection of liner, etc. Also cost of any specialist liner (geomembrane, Butyl, EPDM etc.). |
| Long Term Maintenance |
Generally lower maintenance of the seal itself, since there's no artificial liner, but may require managing seepage, dealing with structural problems, erosion of banks, etc. |
Maintenance required: avoid punctures, UV damage, liner degradation, joint or seam failures. If damage occurs, seepage losses may rise substantially. Also may need underlay, protective geotextiles etc. |
| Lifespan |
Soil or natural clay “lining” (if naturally/clay-rich soil) might hold up well, but suffer in variable soils; water table dynamics may undermine them. |
Liner lifespan varies: synthetic liners often expected to last 20-30+ years if well-installed and protected; natural bentonite or clay sealing might last less or require rework. |
| Cost per m³ of stored/usable water |
Lower initial cost, but because of seepage losses, cost per usable m³ (over years) rises. Over time the water lost can make the unlined reservoir more expensive in terms of water “you actually get to use.” |
Higher upfront cost, but with much better retention, cost per usable m³ tends to be lower over the life of the reservoir, especially in dry years or where rain is intermittent. |
Quantitative examples of lined reservoirs
In a study of irrigation canals in Pakistan they found that unlined canals had average seepage losses around 19%, whereas lined canals had much lower losses (e.g. ~2-6%) depending on lining type and condition.
Another canal study showed lining can reduce seepage by ~78% compared to unlined condition. IWA Publishing From a UK report (“Water for Agriculture”, Fens for the Future, Cranfield etc): when comparing lined vs unlined reservoirs (medium size), lined ones have higher costs per m³ of stored water but deliver more usable water (i.e. lower effective cost per usable water when factoring losses).
In conclusion
Rainwater harvesting reservoirs offer a reliable supply of water with a better control of storage volume where reservoirs are lined.
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Better control over storage volume.
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Improves cost effectiveness over life of reservoir if water is scarce or has high opportunity cost.
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Reduces risk of reservoir failure from seepage affecting banks, undermining structure.