General Document

WATER CONTROL (SOUTH EAST)

Reservoirs

There are 15 reservoirs that supply the bulk of water supply for navigational purposes in the South East. There are 2 hydrological areas within the South East:- 1) Oxford / Grand Union (OX/GU) – which compromises the Braunston, South Oxford, GU Leicester Line and Saddington ‘sub-groups’ of reservoirs. 10 in total 2) Grand Union South (GUS) – compromises the 5 reservoirs in the Tring Group. Together they have a capacity of 7,110 Mega litres (ML) – each ‘mega litre’ equates to 1000 cubic metres or 220,000 gallons.

Only 80% of this total capacity is usable – on the basis that there is a minimum level that reservoirs can be drawn due to ecology and SSSI (Site of Special Scientific Interest) requirements.

This ‘usable’ capacity, in itself, is not sufficient to satisfy the needs throughout the whole boating season – additional rainfall is always necessary. Hence a dry spring / summer can result in problems even if the balance in reservoir were high at the start of the season.

Other sources of water? Reservoirs are not the only source of water, there are three main others 1) River feeds. Several rivers flow into the canal to top up and provide inflow:- - River Swift - River Ouse - River Cherwell

2) Boreholes – the two significant ones are on the GUS at Cowroast and Northchurch. The amount that can be extracted over the year is monitored and regulated by the Environment Agency. We have become expert on extracting to the limit over the course of the season. 3) Fresh water springs – The main flow is from Wendover springs (at the end of the disused, in part, Wendover Arm). A pipeline is sunk within the ‘dry’ section to facilitate the flows.

What monitoring do we undertake? Two main types:- a) We monitor water levels and rate of use of reservoirs and . b) Monitoring stations are positioned around the network. We refer to this modern system of monitoring as the ‘SCADA’ system – you will see the black boxes positioned around the network and at lock sides.

Page 2 of 22

The SCADA system gives us on going information on water levels (at the monitored location) and also at key lock locations.

The ‘lockage’ information tells us how frequent boats are using that part of the network – and we translate this into volume of water used so we can make predictions within our water modelling.

Water level information allows us to monitor remotely and based on high or low water levels alarms are triggered that our maintenance teams respond to accordingly.

There are 27 locks that are monitored across the South East network (there are 240 locks in total) and there are 97 locations where SCADA equipment monitors water levels.

What part do Backpumps play? There are 47 Backpump locations across the South East this is approximately 50% of all backpumps installed across England and Wales.

There has been increased investment over the last 20 years as a result of water shortages experienced in the mid 90’s on the Oxford and Grand Union Canals.

Backpumps are designed to recirculate water uphill ie. around control the lock/lock flight they are not designed to transfer water over significant distances.

Increased sophistication / automation of backpumps linked to SCADA (level) monitoring now ensures that over 50% of water used at ‘backpump sites’ is recirculated.

Efficiency of backpump operation clearly avoids drawing down water from reservoirs and has been particularly effective over the last 3 years during early months of the boating season.

What part can lock keepers play in water conservation? Simply put – a hugely important role.

Lock keepers, can at the strategically important locations deployed manage throughput of boats so that water use is optimised:- a) Maximising times when (for broad locks) 2 boats use the same lock full of water b) Marshalling boats to wait for locks to be ‘set’ in their favour. During the drought we asked for boats to wait upto 45 mins for another boat (to join them) or for the lock to be set in their favour. c) Specifically helping boaters through difficult lock flights (e.g Foxton & Watford) where greatest risk of abuse exists. d) Explaining water conservation measures to passing boaters which in turn results in boaters following responsible behaviour. e) Ensuring no paddles are left up – which would waste water f) Explaining why restrictions are necessary / sometimes necessary g) Generally adding positively to the boating experience

Page 3 of 22

How have reservoirs fared over the last 2 years?

% Reservoir Group Holdings (South East) 2011 2012 2013 Start End Start End Start (Est) OX / GU Braunston 91 23 60 93 95 South Oxford 97 31 85 32 95 GU Leicester 83 7 31 99 95 Saddington 99 17 40 100 95 Grand Total (Ox/Gu) 90 19 54 79 95 GU South Total 89 76 58 61 88