Water Resources of the Victoria River District
Tickell, S. J. (Steven); Rajaratnam, L. R. (Lakshman)
Northern Territory. Department of Lands, Planning and Enviroment. Water Resources Division
E-Publications; E-Books; PublicationNT; Report no. 11/1998
Victoria River Region
The aim of this study is to map, describe and evaluate the region's water resources. The project was started in 1993 at the request of the Victoria River District Conservation Association (YRDCA) and it was funded jointly by Landcare, the NT Government and the purpose is to provide pastoralists and communities with water resource information that will assist with property planning. VRDCA.
Groundwater -- Northern Territory -- Victoria River; Water-supply -- Northern Territory -- Victoria River; Water resources development -- Northern Territory -- Victoria River
Northern Territory Government
Report no. 11/1998
33 pages : illustrations and maps ; 30 cm.
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
https://hdl.handle.net/10070/672982 [Water Resources Survey of the Western Victoria River District - Water Resources of the Victoria River District_WRD98011.pdf]; https://hdl.handle.net/10070/672981 [Water Resources Survey of the Western Victoria River District - Water Resources of the Victoria River District_WRD98011.pdf]
Technical Report WRD98011 Viewed at 15:07:47 on 29/07/2010 Page 25 of 37. , The catchment area of a drainage-line tank is small and for design purposes an area of 2 kmor less is adequate. The off-stream tank requires a minimllm catchment area between 4 and 8 km2 Strearns with catchment area more than 30 km2 would have the potential of providing water to more than one excavated tank en route. Site investigalions and construction Usually an initial site is chosen based on where the water is needed and where sufficient ,vater wi!! be able to be captured. Following that, detailed site investigations are recommended before excavation begins. These will determine if there is sufficient depth or material which can be economically excavated and whether or not significant leakage will occur. Simple soil tests which can give this information are detailed in Technical report L2!! 9980 (*3). SUSTAINABILITY OF WATER STJPPLIES \Vater supplies are obviously directiy dependant on rainfall, $0 a knowledge of past climatic variations is eSSential in determining if present levels of water usage call be maintained. The VRO covers a vast area and spans the humid and semi-arid climatic zones. As a consequence it experiences considerable variation in raintall. both across the area and ,>vith time. In a particular season some regions can receive above average rainfall wh.iIe others can be below their respective averages. Figure 10 illustrates lhis by comparing long term annual rain till from two stations. 'Nave Hill in the southern VRD and Rosewood in the north. Longer term cycles of drought and wet periods are also apparent. ~lajor droughts have occurred in the past. for example during the late 1920's and 1930s. On a broad scale. the pattern of wet and dry periods is similar across the region but in detail one area cm be in drought while another is not It is important to note that the period trom the early 1970's to the present has been relatively wet compared to the preceding record. In view of the variability of rainfalL several points are now discussed: How do droughts sp..:diically aftect difkrent water sources? Can present levels of ,vater usage be sustained dllring droughts" and 'vVhat measures can be taken to lessen the effects of drought" EFFECTS OF DROUGHTS ON HA.TER SOURCES Groundwater levels respond in varying degrees to the pn:ccding seasons rainfall or lack of it. Most aquilers in the VRD are of the lractured rock type with limited storage in comparison with the more extensive type of aquifer tound elsewhere. Observations made at Rosewood and Lajamanu suggest that recharge and thus a rise in water level will only occur if rainfall is above the average. Spring nows and water levels in bores and wells are both directly at1ected by water table lluctuations. If levels drop sufficiently, bores may have insufficient water above the pump inlet to maintain the nomlal pumping rate. In the extreme case of shallmv bores and wells. they can potentially dry up completely if the \vater table tails below the slots in the casing or the base of the well. The eiteet on springs wOllld be to reduce the duration and amount of flow. Similarly spring fed waterholes would not last tl)[ as long as during normal seasons. The effect of drought on dams and non-spring feu waterholes is obviously that they may not be replenished as often as normal and in extreme cases will not be replenished at all for several seasons. 21