10 - SURFACE WATER QUANTITY Summary RPS Objectives • The maintenance of the flows and levels in significant streams, rivers, lakes and wetlands to preserve their natural character and to protect high ecological, cultural or scenic values. • The maintenance of water flows and levels in natural water bodies that are sufficient to preserve their life-supporting capacity, natural character, intrinsic values and associated or dependent values. • The efficient use and conservation of water resources. • To protect property and other values from adverse effects due to the diversion of water from its natural drainage pattern. Pressures • Northland’s water resources are under increasing pressures to meet demands from a variety of consumptive users – including agriculture, horticulture, public and private water supply and industry sectors and the effects of land use change. • Surface water takes, both consented and permitted, affect water flows. There is an increase in the number of permitted takes in Northland, as well as a large number of ‘permitted’ takes that are likely to exceed the volume allowed in the permitted activity rules. • Currently there are 381 consents allocated up to 500,000 m3/day of water from streams, rivers and dams in Northland (excluding diversions). A review of consented water takes indicates many catchments in central and southern areas of Northland are highly allocated. State • Annual rainfall ranges from 900mm in low-lying coastal areas to over 2900mm at higher altitudes. • Flows vary greatly between catchments, which can be largely attributed to rainfall patterns, catchment size and catchment geology. In Northland, catchment geology greatly influences low flows during drought conditions. • Northland's climate is such that it will experience a regional drought, on average, once every three years at east coast and inland locations, and once every four years at west coast and high altitude locations. Northland Regional Council 2007 State of the Environment Report 192 10 – Surface Water Quantity Doing well • The Regional Water and Soil Plan contains policies relating to the maintenance of flows and levels in water bodies. • The Northland Regional Council (NRC) operates a hydrometric network consisting of 60 sites throughout Northland, which collects continuous data for 30 river level sites, six tidal monitoring sites and 24 rainfall sites. • During periods of drought, water levels are monitored and when a low threshold is reached a low flow-gauging programme is undertaken in affected rivers. The NRC holds more than 11,700 flow-gauging records for 1503 Northland sites. • New flow measuring equipment, an Acoustic Doppler Current Profiler has improved the council’s ability to gather more accurate information on Northland rivers, in both low flow and flood conditions. Areas for improvement • Ensure accurate water metering of consented takes and water use analysis to enable a better understanding of the volume of water abstracted within catchments and the effects on water resources. • Encourage all water users to register their ‘permitted takes’ with the Council to enable greater understanding of the ‘actual’ water taken in catchments. • Establish design minimum flows (minimum flow required to be maintained) for a greater number of catchments. • Include in Northland’s plans maximum total volumes allocatable for water bodies in Northland, to provide water use securities for users and sustainable allocation of water resources. Also include rules to ensure assessment of cumulative effects of subdivision on water resources. Northland Regional Council 2007 State of the Environment Report 193 10 – Surface Water Quantity 10.1 Introduction The Northland Regional Council has responsibilities under the Resource Management Act 1991 (RMA 1991) to control water use, and to monitor the level and flow of water bodies. Successful management of the water resources will stem directly from informed resource management decisions. This can only be achieved from accurate knowledge of the environment itself, including climate, water quantity, present water use and potential demand for water in Northland. The Council may also control the use of land for the purpose of maintaining sufficient water flows for human uses and aquatic life. Natural water quantities are directly related to rainfall, soils, vegetation and groundwater. Some rain seeps into the ground and becomes part of the groundwater system, while the rest flows over the land to our streams and rivers that discharge into the coastal environment. The Waipoua River. Regional Policy Statement objectives The Regional Policy Statement for Northland (NRC 2002a) contains a range of objectives relating to the quantity of Northland’s surface water resources. These objectives seek to maintain flows, conserve water resources, and protect the natural environment from adverse effects. The Regional Policy Statement (RPS) objectives are: • The maintenance of the flows and levels in significant streams, rivers, lakes and wetlands to preserve their natural character and to protect high ecological, cultural or scenic values. • The maintenance of water flows and levels in natural water bodies that are sufficient to preserve their life-supporting capacity, natural character, intrinsic values and associated or dependent values. • The efficient use and conservation of water resources. • To protect property and other values from adverse effects due to the diversion of water from its natural drainage pattern. Northland Regional Council 2007 State of the Environment Report 194 10 – Surface Water Quantity Environmental results anticipated The following is the anticipated environmental results after the implementation of the water quantity policies in the RPS: • Protection of important freshwater habitats, particularly natural wetlands from reductions in surface water and ground water levels. • Preservation of the natural character, intrinsic, ecosystem and amenity values of natural water bodies to the extent that these depend on water levels and flows. • Protection of the values of water bodies held by tangata whenua. • Sustainable and efficient use of the water resources of Northland • Increased awareness of water conservation and the greater implementation of water conservation practises. • Minimisation of actual and potential damage to property from damming, diversion and discharge of run off. Northland Regional Council 2007 State of the Environment Report 195 10 – Surface Water Quantity 10.2 What are the pressures on water resources? Demand for surface water Northland’s water resources are under increasing pressure to meet demands from a variety of consumptive users. These users include the agriculture, horticulture, domestic water supply and industry sectors. Taking water for these sectors must be considered against the ability of the water to maintain its life-supporting capacity for aquatic life, aesthetic value and the spiritual and cultural value of water to tangata whenua. Lower water levels can result in increased water temperatures, depleted dissolved oxygen levels, increased algal growth and general degradation of water quality. Low water levels also reduce the ability of water bodies to assimilate waste. Different uses and values are not always compatible, particularly during summer months when there is less water available. To ensure that conflict between the use of water resources and the potential for adverse effects from excessive uses are decreased, efficient use of water must be promoted. Water resources are managed through the RMA 1991, regional plans and resource consent process. Surface water availability within the region is affected by consumptive water use, including surface water takes, dams and diversions, and culverts and fords. Pressures are also placed on lakes and wetlands, with land use change having an impact on most aspects of water quantity. There are more consents for surface water takes than groundwater takes in Northland, with a much higher volume of water allocated from surface water as shown in table 1 (below). For more information on groundwater takes refer to the groundwater chapter of this report. Table 1: Source of water allocated in Northland. Note: figures are approximates. Rivers, lakes and springs Dams Groundwater Percentage of consents 46 10 44 Percentage of allocated 50 25 25 daily volume (m3/day) Consented surface water takes Northland Regional Council requires resource consents for most major surface water takes, with the exception of farm water supplies which have traditionally been authorised as permitted activities. There are 381 consents allocating approximately 500,000 m3 of water per day from streams, rivers and dams in Northland (excluding diversions). This excludes the Wairua Power Station take, as this is a consent to take, divert and discharge up to 2,592,000 m3 per day. Over 60 of these consents are for the expansive Wairua River Catchment as shown in figure 1 (below). This does not include surface water takes authorised as permitted activities under the Regional Water and Soil Plan (RWSP) for Northland (NRC 2007) such as smaller takes for farms, lifestyle blocks and domestic supplies. The number of consents has decreased by about 35 with a reduction in total water allocated of 60,000 m3/day since the 2002 SOE report (NRC 2002b). However, errors in calculating total allocation in 2002 are likely to have occurred due to inconsistent recording of total volumes of water allocated. In addition more efficient allocation has Northland Regional