The basic question which this thesis seeks to answer is: 'Was the baseflow which flowed continuously in Lockyer Creek prior to 1980 outflow from adjacent alluvial aquifers or was it outflow from basalt aquifers on the Main Range?' This question was not obvious at the start of the project when information from 'official' sources suggested that Lockyer Creek was ephemeral, and there was no baseflow.To answer this question, it was necessary to define baseflow (as outflow from aquifers) and to devise a means of separating it from overland flow, because the existing methods separate 'quick flow' from 'prolonged flow': not overland flow from baseflow. The existence of baseflow presumes the existence of aquifers in the catchment, so geology of the catchment was examined to identify its aquifers.Streamflow records at four sites: three upstream and one downstream, were analysed to establish that baseflow was a significant component (25%) of streamflow over the period 1910-2000, and that average baseflow over this period was close to the estimated long-term safe yield of the Lockyer alluvium. The process of aquifer recharge was analysed and it was concluded that the alluvial aquifers are recharged by infiltration of water mainly through the bed of creeks and saturated flow in the aquifer below the water table, followed by unsaturated flow across a saturated/unsaturated boundary at the wetting front. Saturated flow is driven by the hydraulic gradient on the water table (which was shown in 1949 to slope away from creeks) while unsaturated flow is driven by the matric potential across the wet and dry sides of the front. Unsaturated flow is orders of magnitude slower than saturated flow but takes place over a much greater area than saturated flow. Because it is such a slow process, long duration flows are required to achieve significant aquifer recharge. Chemical analyses of water from basalt aquifers, baseflow and alluvial aquifers confirmed that the 'ionic signature' of the three waters was similar, which would be expected if baseflow was outflow from basalt aquifers, which in turn recharged alluvial aquifers. The ionic signature of water in the adjacent sandstones is quite different from that of these three waters. Ions present in water in the alluvium, including the sodium vii Glossary Adsorbed water: The water held in soil by surface-attractive forces: the attraction between unlike charges, such as the positive charges on hydrogen ions and the negative charges on oxygen ions. Generally, the more surface (the more clay and organic matter) a soil has, the greater is the amount of adsorbed water.Aquifer: A saturated permeable geological unit that can transmit significant quantities of water under ordinary hydraulic gradients (Freeze and Cherry 1979); a geological unit which contains water and transmits it from one point to another in quantities sufficient to permit economic development (Linsley et al. (1982). It is suggested that, for a lithologic unit to be considered to be an aquifer, it should have a hydraulic conductivit...
by one half compared with plots subjected to dry spells of 7 days.Nedulation and nitrogen production in tops were similarly affected. Thus, for the species tested, the response to irrigation was much greater with the legume than with grasses. and without mulch, imder a range of w a t e r i n g frequencies a t t h e f i r s t isampling. 1533.10. Mean number of nodules recovered from s i r a t r o a t t h e f i r s t sampling, from p l o t s w i t h and without mulch, and grown under a range of watering f r e q u e n c i e s . 155 3.11u R e l a t i o n between nodule number and nodule weight a t t h e f i r s t asampling. 1^6^ . 1 2 . R e l a t i o n s h i p of weight of n i t r o g e n i n tops:; (g.)and volume of nodules; (mli) a t t h e second sampling. 157 3.13* Diagrammatic r e p r e s e n t a t i o n of mean diy m a t t e r production per day from l u c e r n e and s i r a t r o i n t h e second s e a s o n . Shallow soils exaegerate this stress con.ition which is likely to occur eveil when soil moisture supply is 600d.An important feature of a water harvesting project is that its irrieated pastures rely on runoff for their water supply, and such runoff is erratiic; -depending on such things as rainfall intensity and duration, slope of the land, surface cover, infiltration rate, antecedent soil moisture, and catchment area. Generally, however, it.could be expected that a water supply should become available in the summer storm season (December to March), and that irrigation could be carried out in autiann, winter, and spring when native pastures are at their worst for animal production.However, periods will occur when no irrigation water is available, and plants will then suffer from high water stress, and possibly desiccation. This could be common in early summer, when the storage ha,s been emptied by prior irrigation, and is awaiting replenishment. Plants without good drought resistance could not withstand these conditions, and so would not be suitable components of perennial pastures unless they had good re-seeding capabilities.Areas which may be irrigated from dajns are generally fairly small in extent, so that animals Trould not normally be grazing on the irrigated area all the jear round.Hence, it would be best to use the area to provide forage when it is most needed -i.e. autumn, winter, and spring. Management to provide a balanced pasture ma,y not be required, as it may be more convenient to allow animals to graze on the irrigated area for only conditions. An improved strain of rhodes grass was used as the compajiion species as; methods of establishing legumes in kikt^ru had not been studied, and after the experience with experiment Al it was expected that rhodes grass would invade the area. The productivity of these mixtures was measured over a period of two years, and, following a further period of two years daring which time plants were subjected to severe drought conditions, persistence of the species was ol^erved. II REVIEW OF LITERATUREA. THE CLIMATE AT LA.WES.
The basic question which this thesis seeks to answer is: "Was the baseflow which flowed continuously in Lockyer Creek prior to 1980 outflow from adjacent alluvial aquifers, or was it outflow from basalt aquifers on the Main Range?' This question was not obvious at the start of the project when information from 'official sources' suggested that Lockyer Creek was ephemeral, and there was no baseflow.
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