5.0. WATER QUANTITY
AIMS: Increase water attenuation, slow run-‐off, improve resilience to low flows and increase aquifer re-‐charge.
5.1. What are the issues? Abstraction and low flows The Test & Itchen supply much of Hampshire’s public water needs, including a large proportion of the Isle of Wight’s requirements. There are a number of significant surface water abstractions as well as groundwater abstractions from the chalk. The catchment also supports a large number of commercial fish farms and watercress growers who are dependant on reliable and abundant water supplies. Although the majority of abstraction is non-‐consumptive and returns water locally the overall impact of abstraction puts pressure on flows and can potentially lead to rivers not having enough water to support a healthy ecosystems. Flooding With changes in climate affecting rainfall patterns and larger areas of land being covered for development and thus loosing their natural ability to drain water, flooding has become an increasingly apparent issue in recent years. Groundwater flooding is a particular problem for many parts of the catchment and following heavy rainfall events it is often exacerbated by surface water flooding. 5.2. Where are the pressures? There are a number of locations in the catchment landscape where a reduced ability to maintain base flows during periods of low rainfall will exert a negative impact. Water quantity has a direct bearing on the effluent volumes that can be discharged from point sources of pollution, where sufficient flows are needed to ensure the effluent is diluted appropriately downstream. Abstraction licenses for drinking water supplies also depend on maintenance of sufficient base flows and similarly, rivers and streams require sufficient flow during dry periods to remain in good ecological condition. At the other end of the spectrum, there are many locations where the unregulated release of water from the land and into our rivers can pose a threat to people living in the catchment and cause community disruption. In addition to residential properties there may also be locations where important buildings and other critical infrastructure are at risk of flooding. The properties and infrastructure at risk of being flooded are shown in Figure 26 which cross-‐references settlements against flood risk zones and surface water flood risk areas to identify where there is a risk of flooding and damage to property or threatening human health and safety.