Over the next 35 years there will be a slowing down of population increase, followed by a period of no growth and eventual negative growth. The changes in population are not occurring uniformly through the region or uniformly through settlements. Generally the rural population is experiencing a more rapid slow-down in growth than the urban populations but there is also a shift in the “centre of gravity” of the Blenheim- Renwick and the Picton-Waikawa urban areas. The main urban growth areas are the green-field sites on the periphery of existing urban areas. This has a significant impact on stormwater service design particularly for areas that drain through existing urban areas and existing infrastructure. This is an issue for Blenheim. The urban growth pockets have been identified to the north and west of the existing town. The natural drainage path is from west to east. Design of stormwater systems will have to take into account the impact on existing downstream residents. The growth projections are included in the Blenheim Stormwater Strategy and techniques to maximise surface water infiltration and balancing flows through detention storage areas are important tools to limit the downstream impact. The number of inhabitants per dwelling is also falling. This means the demand for housing will decline at a slower rate than the fall in population. However it may also mean that; the wealth per household declines at a higher rate. When planning services with a long lead time the increase in demand needs to be anticipated with a margin of error. A ‘just in time’ approach is prudent both from the point of view of cash flow and the uncertainty of the rapidly changing environment. Conversely, from a financial planning prospective it is prudent to anticipate a slower growth in the rateable property base and development contributions and a subsequent delay or reduction in revenue. On the other hand, many infrastructure assets have a planned life in excess of 80 years and as a large proportion of the total costs are in the initial construction and it would be very expensive to under-estimate demand in the long term. Thus we should; err on the high side for such life components, use the medium scenario for shorter life components, and for all; build “Just In Time”. Further Population growth is probably the most obvious and ubiquitous influencing factors for the projecton of future services. owever popuation growtalone s a poor indicator of demand for infrastructural services. Other underlying factors such as climate change, environmental standards, national legislation, major hazard resilience, levels of service and other social aspects often have a far greater impact either alone or in combination. There is less empirical data to support assumptions relating to these factors. However it is important these are also placed on a common footing and a consistent approach underlies medium term strategy development. 3.2.2 Demand Forecasts Marlborough Urban Growth Strategy In 2009 the Council embarked on a major project to develop a comprehensive urban growth strategy for Marlborough region. At that time the population projections based on previous census were estimating growth over the next 25 years of approximately 9,300 additional residents across the region. The population estimate was used to inform a major consultative process with both the public and council staff and other expert stake holders. The quantity of land required was evaluated and areas with potential to be developed into urban growth pockets identified. Underlying the project it was assumed that growth would occur around existing settlement nodes. The Canterbury earthquakes occurred during development of the strategy and early drafts had to be revised after and land around Blenheim, particularly to the east, was assessed as susceptibility to liquefaction and lateral spread. The final strategy document was accepted by council and published in March 2013. The strategy forms a valuable platform for planning future capacity upgrades to all services. Page 29