Question: Which lake in Northern Ireland is near the Ballyscullion House and supplies 40% of Northern Ireland's water?

Context articles: Fivemiletown Creamery
Northern Ireland Water
Ballyscullion House
Northern Ireland Football League Cup
Recycling in Northern Ireland
Lough Neagh
Swim Ireland
River Vartry
Silent Valley Reservoir
BBC One Northern Ireland

Fivemiletown Creamery is based in Fivemiletown, County Tyrone, Northern Ireland, and is a producer of handmade speciality soft cheeses and cheddars The company is a farmers' co-operative, and employs around 40 people.
 The creamery draws its milk supplies mostly from over 60 dairy farmers from across Northern Ireland.
 The company was founded in 1898 and added cheese production in 1972.
 Fivemiletown Creamery is the only speciality cheese maker in Northern Ireland.
Northern Ireland Water Limited (Irish: "Uisce Thuaisceart Éireann" ; Ulster-Scots: "Norlin Airlan Wattèr") is a water company in Northern Ireland.
 Formerly an executive agency (the Northern Ireland Water Service) within Northern Ireland's former Department for Regional Development, it became a government-owned company on 1 April 2007.
 The company provides 625 million litres of clean water a day for almost 1.7 million people as well as treating 134 million m of wastewater every year, and has approximately 1,400 staff.
 It is responsible for 26,500 km of watermains and 14,500 km of sewerage mains, as well as 47 water treatment works and 918 wastewater treatment works.
 In 2005, the Water Service had an annual budget of £302 million and fixed assets of £4.9 billion.
Ballyscullion House refers to two country houses built for the Hervey family near Bellaghy in County Londonderry, Northern Ireland, close to Lough Beg at north-west corner of Lough Neagh.
The Northern Ireland Football League Cup, also known as the Irish League Cup, and the BetMcClean.com League Cup is a national football knock-out cup competition in Northern Ireland open to the 40 Northern Ireland Football League clubs.
 It is the third-highest rated competition in domestic Northern Irish football after the NIFL Premiership and Irish Cup.
 It should not be confused with the Irish League Floodlit Cup which ran from 1987–88 to 1997–98 initially under the sponsorship of Budweiser and latterly Coca-Cola.
 Unlike the Irish Cup, the competition does not have a berth for UEFA Europa League qualification, however the winners qualify for the next season's all-Ireland Setanta Sports Cup.
 The cup is operated by the Northern Ireland Football League, who in 2013 took over the administration from the Irish Football Association (IFA) for the 2013–14 season onwards, after which the cup was renamed as the Northern Ireland Football League (NIFL) Cup.
Roughly 40% of waste is recycled or composted in Northern Ireland.
 Northern Ireland's local councils have statutory responsibility for the collection and disposal of waste, and as such are the lead actors in promoting recycling.
 Since 2000, when the Northern Ireland Department of the Environment published its first Waste Management Strategy, local councils have come together to form three separate subregional waste management partnerships: arc21 (consisting of councils in the east of Northern Ireland), the North West Region Waste Management Group, and SWaMP (the Southern Waste Management Partnership).
Lough Neagh (pronounced , ) is a large freshwater lake in Northern Ireland.
 It is the largest lake by area in the British Isles, with a surface area of 392 km2 .
 It supplies 40% of Northern Ireland's water.
 Its main inflows are the Upper River Bann and River Blackwater, and its main outflow is the Lower River Bann.
 Its name comes from Irish: "Loch nEachach" , meaning "Eachaidh's lake" (] ).
 The lough is owned by the Earl of Shaftesbury.
Swim Ireland (Irish: "Cumann Snámh Éireann" ) is the national governing body of swimming, diving, water polo, open water swimming and synchronized swimming in the island of Ireland (Republic of Ireland and Northern Ireland).
 Competitors from Northern Ireland can opt to compete for British Swimming in international competitions, with the exception of the Commonwealth Games where they can compete for Northern Ireland.
The River Vartry (Irish: "Abhainn Fheartraí" ) is a river in the Republic of Ireland.
 It rises in "Calary Bog" under the Great Sugar Loaf mountain in north County Wicklow.
 In 1861 Parliament passed the Dublin Waterworks Act creating the project to dam the River Vartry in Roundwood to form the Vartry Reservoir.
 This was completed in 1865 and was the first clean source of water for Dublin, replacing the canal water.
 There are several references to the Vartry in James Joyce's "Ulysses", "… and on his expressed desire for some beverage to drink Mr Bloom in view of the hour it was and there being no pump of Vartry water available for their ablutions let alone drinking purposes...” or “Power.
 Particular about his drink.
 Flaw in the glass, fresh Vartry water.”
 This reservoir still supplies 40% of all of Dublin's water needs.
The Silent Valley Reservoir is a reservoir located in the Mourne Mountains near Kilkeel, County Down in Northern Ireland.
 It supplies most of the water for County Down, surrounding counties and most of Belfast.
 It is owned and maintained by Northern Ireland Water Limited (formerly DRD Water Service).
 The reservoir was built between 1923 and 1933 by a workforce of over one thousand men, nine of whom died.
BBC One Northern Ireland is a television channel operated by BBC Northern Ireland.
 It is the Northern Irish variation of the UK-wide BBC One.
 The service is broadcast in Northern Ireland from Broadcasting House in Belfast.
 Outside Northern Ireland the service is available on Sky (UK) channel 953 and across the border in the Republic of Ireland on Sky (ROI) Channel 141.