<h2>JANUARY 2016</h2>
Portsmouth Water has no large raw water storage reservoirs.  It relies almost entirely upon groundwater reserves in the chalk aquifers of the South Downs and abstracts its raw water from wells, boreholes and springs.  It has one river abstraction at Gaters Mill on the River Itchen, a chalk river with a groundwater baseflow.

Those reserves rise and fall with the seasons and so Portsmouth Water pays particular attention to the local hydrogeological data by monitoring rainfall at its Havant Offices, groundwater levels in the chalk at Idsworth on the Hampshire/Sussex border, as well as the total yield from the natural springs at Havant and Bedhampton.

These resources are monitored on a daily basis and reported upon on a monthly basis.  The information here is therefore at times one month behind the most current situation.

The information gathered is reproduced here for information purposes; no guarantee is given as to its accuracy.
<h2>Rainfall at Havant</h2>
The Rainfall Records at the Company’s Head Office at Havant date back to 1886.

The month of January saw approximately 190% of the long term average rainfall for the month.  Rain fell on approximately 80% of the days with the maximum daily rainfall on Sunday 10 January of approximately 24mm.

<a href="https://www.portsmouthwater.co.uk/wp-content/uploads/2016/02/rain.png"><img class="aligncenter size-large wp-image-3960" src="https://www.portsmouthwater.co.uk/wp-content/uploads/2016/02/rain-1024x550.png" alt="rain" width="1024" height="550" /></a>

Total rainfall for the month was 162mm, lower than the long term average (last 30 years) of 85mm.

<a href="https://www.portsmouthwater.co.uk/wp-content/uploads/2016/02/rain2.png"><img class="aligncenter size-large wp-image-3961" src="https://www.portsmouthwater.co.uk/wp-content/uploads/2016/02/rain2-1024x587.png" alt="rain2" width="1024" height="587" /></a>
<h2>Groundwater Levels at Idsworth</h2>
The Company has groundwater records from the Idsworth Estate Well, north of Rowlands Castle, which date back to 1931.  Water levels in the Well, which is entirely unaffected by abstraction, give an accurate indication of the groundwater reserves of the South Downs.  In the winter, levels usually rise in response to rainfall, whilst during the summer, levels recede as any summer rainfall either evaporates or is taken up by trees and plants before reaching the aquifer below.  Levels can fluctuate by as much as 20m.

The Groundwater level is usually recorded in metres AOD (Above Ordnance Datum), Ordnance Datum principally being equivalent to sea level.

At the end of December groundwater levels were close to the long term average as a result of average Autumnal rainfall.  The high rain fall of January has seen groundwater levels rise approximately 6m above the long term average and therefore considered to be ‘high’ in comparison to the average levels.

The graph below shows the change in groundwater level over the last twelve months compared to the Long Term Average (last 30 years).

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