[one]
<h4>2015</h4>
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.

<em>The information provided in this section shows the Water Supply data for the 12 months from April to March. The monthly data for our resource levels can be found <a href="https://www.portsmouthwater.co.uk/category/water-supply-news/">here</a>.
</em>

[/one]

[divider height="30" style="none" line="default" themecolor="1"]

[accordion title="" open1st="0" openAll="0" style=""]

[accordion_item title="Rainfall"]

Last year’s rainfall was characterized by the variable levels compared with the 30 year long-term average.  The months of April, August, October, November and January saw rainfall levels exceeding the long-term average by up to almost 200%, whilst June, July, September, December and March with levels below the long-term average with September being particularly dry with only 8mm of rain.  Annual total rain was however, 813mm compared with a long-term average of 774mm.

<img class="aligncenter size-full wp-image-3289" src="https://www.portsmouthwater.co.uk/wp-content/uploads/2015/02/rainfall-2015.png" alt="rainfall-2015" width="594" height="349" />

[/accordion_item]

[accordion_item title="Groundwater Levels"]

The Company has monitored the groundwater level at Idsworth Well, Rowlands Castle, for many years since the well is unaffected by abstraction and is representative of groundwater conditions in the South Downs chalk.  Around 85% of Portsmouth Water’s abstractions are from underground sources and so groundwater levels are critical to maintaining supplies.

Groundwater in the local aquifer normally fluctuates approximately 9.5m between maximum and minimum annual levels.  Groundwater levels in the Spring of 2014 were approximately 7m above the long-term average as a result of the heavy rain of December 2013, and exceptional rain of January and February 2014.  Groundwater rose to 35.5, in February, the second highest level recorded in the month of February since records commenced in 1932.  As is normal, groundwater levels fell in the Spring and Summer and the exceptionally dry September saw groundwater levels recover slightly later than normal.  By March 2015 levels were approximately 0.8m above the long term average.

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

<a href="https://www.portsmouthwater.co.uk/wp-content/uploads/2015/02/idsworthwellleveltoJune2015.jpg"><img class="aligncenter size-full wp-image-3750" src="https://www.portsmouthwater.co.uk/wp-content/uploads/2015/02/idsworthwellleveltoJune2015.jpg" alt="groundwater" width="919" height="612" /></a>

[/accordion_item]

[accordion_item title="Abstraction"]

Abstraction from the Company’s various sources in 2014/15 was as shown in the table below:

<img class="aligncenter size-full wp-image-3291" src="https://www.portsmouthwater.co.uk/wp-content/uploads/2015/02/table.png" alt="table" width="789" height="785" />

[/accordion_item]

[accordion_item title="Treated Water Distributed"]

<img class="aligncenter size-large wp-image-3292" src="https://www.portsmouthwater.co.uk/wp-content/uploads/2015/02/distributed-1024x630.png" alt="distributed" width="1024" height="630" />

<img class="aligncenter size-full wp-image-3293" src="https://www.portsmouthwater.co.uk/wp-content/uploads/2015/02/input.png" alt="input" width="890" height="495" />

The annual average distribution input dropped from 171.5 Ml/d in 2013/14 to 168.8 Ml/d to 2014/15.  The volume of water distributed is influenced by many things, including the weather.  The peak week of 202.0 Ml/d occurred in July due to the warm weather and low rainfall.

Abstraction is drawn from three types of source, the River Itchen Works which treats surface water, boreholes and wells which abstract groundwater from the underground chalk and Farlington Water Treatment Works which treats spring water from Havant and Bedhampton.

Our largest source utilises water from a group of natural springs at Havant and Bedhampton.  Water from the springs is treated at Farlington Water Treatment Works.

The nature of the chalk aquifer of the South Downs ensures that at many sites high quality water is abstracted which requires only minimal treatment.  Some chalk sources are at risk of cryptosporidium oocysts (which can cause severe stomach upsets) being present in the water which require enhanced treatment by membrane filtration.

[/accordion_item]

[accordion_item title="Leakage"]

The leakage recovery programme has made excellent progress and for the full year 2014/15 average leakage was recorded at 28.9 Ml/d. This is within the leakage target agreed with Ofwat but further work is being undertaken to ensure we continue to improve our data.

[/accordion_item]

[accordion_item title="Burst Mains"]

The number of burst mains experienced in 2014/15 was 294, compared to 226 that occurred in 2013/14.  The majority of the bursts occurred on 3”-6” cast iron mains and were generally associated with the swelling and shrinking of clay due to changes in soil moisture and temperature.  The number of bursts normally increases during the winter which was the case in the last year compared to the lower numbers experienced in the winter of 2013/14.

We continue to target mains for renewal based on the impact of bursts on customers.  The graph below indicates the overall reduction of bursts as a result of the renewals programme.  However, severe weather often demonstrates the importance of maintaining mains renewals at an appropriate rate.

<img class="aligncenter size-full wp-image-3294" src="https://www.portsmouthwater.co.uk/wp-content/uploads/2015/02/burst-mains.png" alt="burst-mains" width="754" height="411" />

[/accordion_item]

[/accordion]

&nbsp;