Question: Windeyer County is located between the border with South Australia and a river measuring how long from its source to its confluence with the Murray River?

Context paragraphs:
Windeyer County: Windeyer County is one of the 141 Cadastral divisions of New South Wales.  It is located between the Darling River and the border with South Australia.  The Silver City Highway runs through it.  Coombah Roadhouse is located there.

Murray River Flag: The Murray River Flag is flown from paddle steamers and other vessels in the Australian States of New South Wales, Victoria and South Australia that ply the waters of the Murray-Darling river system.  Little is known about the flag's early history but it may have originated as far back as 1850 when the formation of the Murray River League was announced.  R. W. Beddome, founder of the League, enthused "Up with the Murray flag."  No fragments of the original Murray River Flag are known to exist and three variants have passed down to the present day.

Darling River: The Darling River is the third longest river in Australia, measuring 1472 km from its source in northern New South Wales to its confluence with the Murray River at Wentworth, New South Wales.  Including its longest contiguous tributaries it is 2844 km long, making it the longest river system in Australia.

Murray–Darling basin: The Murray–Darling basin is a large geographical area in the interior of southeastern Australia.  Its name is derived from its two major rivers, the Murray River and the Darling River.  The basin, which drains around one-seventh of the Australian land mass, is one of the most significant agricultural areas in Australia.  It spans most of the states of New South Wales, Victoria, and the Australian Capital Territory, and parts of the states of Queensland (lower third) and South Australia (southeastern corner).  The basin is 3375 km in length, with the Murray River being 2508 km long.

Murrumbidgee River: Murrumbidgee River ( ), a major tributary of the Murray River within the Murray–Darling basin and the second longest river in Australia.  It flows through the Australian state of New South Wales and the Australian Capital Territory.  It descends 1500 m as it flows 1485 km in a west-northwesterly direction from the foot of Peppercorn Hill in the Fiery Range of the Snowy Mountains towards its confluence with the Murray River near Boundary Bend.

Murray River Queen: Murray River Queen is an Australian paddle ship built at Hindmarsh Island in 1974 as a luxury passenger cruise boat.  She was a tourist boat carrying passengers on the Murray River in South Australia.  For many years, her home port was Goolwa where she offered week-long cruises operated by her builders, the Veenstra family.  She was the first of several large boats built by the Veenstras for the Murray River, they later also built the M.V. Murray Explorer and PS Murray Princess.

1956 Murray River flood: The 1956 Murray River flood involved the rising of waters in the Murray River and flooding of many towns in New South Wales, Victoria and South Australia.  The flood occurred due to higher than average rainfalls in Western Queensland and heavy rains in the proceeding three months in the Murray-Darling basin.  Flood waters moved down the Murray and Darling rivers for seven months and peaked between 11 and 14 August at Merbein in Victoria and 12.3 m at Morgan in South Australia.  Some areas were flooded up to 100 km from the natural flow of the river.  The flood was and still is considered the biggest flood in the recorded history of the Murray and described as "the greatest catastrophe in South Australia's history", in spite of no lives being lost.

Hundred of Mobilong: The Hundred of Mobilong is a cadastral unit of hundred on the west bank of the Murray River in South Australia and centred on Murray Bridge.  One of the ten hundreds of the County of Sturt, it is bounded on the east entirely by the Murray River.  It was created in 1860 by Governor Richard MacDonnell from a portion of the former Hundred of the Murray, which covered lands beside the Murray River for more than 300 km of its course from mouth to Waikerie.  It was named after an aboriginal name for the swamplands in the vicinity on the west bank of the Murray.

Murray River National Park: Murray River National Park is a protected area in South Australia located between 180 km and 240 km north east of the Adelaide city centre.  The national park was proclaimed in 1972 "to conserve a significant proportion of South Australia’s floodplain environments which are not represented widely in other reserve systems."  The national park consists of three sections adjoining the Murray River and extending from near Loxton in the south west to near Renmark in the north-east.  The first which is known as the ‘Katarapko’ section is located on the north side of the river between Loxton in the south and Berri in the north.  The second section which is known as the ‘Lyrup Flats’ section is located on the north side of the river midway between Berri and Loxton.  The third section is known as the ‘Bulyong’ section is located on the west side of the river upstream from Renmark.  The national park is classified as an IUCN Category VI protected area.

Spectacle Lake, South Australia: Spectacle Lake is a locality in the Australian state of South Australia located in the Riverland on the northern side of the Murray River about 180 km north-east of the Adelaide city centre and about 16 km northwest of Loxton.  Its boundaries were created in August 1999 along with the selection of its name which was derived from the Spectacle Lakes, a lake system which is situated within the locality on the floodplain of the Murray River.  In 2014, a portion of Spectacle Lake was removed and added to the adjoining locality of Loveday to ensure the full extent of Nynes Island is within Loveday.  As of 2012, the land use within Spectacle Lake was divided between conservation and agriculture with the former being concerned with the floodplain.  Spectacle Lake is located within the federal division of Barker, the state electoral district of Chaffey and the unincorporated area of South Australia.

Supporting paragraphs: Windeyer County Darling River
Answer: 1472 km