Salinity

document A Study of Lake Wyara, an episodically filled saline lake in southwest Queensland, Australia
Lake Wyara lies on a tertiary fault, but is much modified geomorphologically by wind and subsequent wave action from the west, so that the eastern shore is smoothed and lined by beaches at various levels, but there is no lunette. When full and overflowing, which has occurred 4–5 times in the last 108 years, it is 3400 ha in area and ca 6m in depth. Most overflows are due to floodwaters from the adjacent Paroo catchment entering the lake via its outflow and then returning again back to the river. During 1987–96, it completely filled and dried once, salinity varying from 2.8 to 350 g L−1. Water was clear, alkaline and strongly dominated by Na and Cl-ions. Macrophytes grew abundantly offshore at lower to moderate salinities, fish were few in variety and limited to low salinities, and waterbirds were usually both diverse and numerous. During the 10 years of study, only 13 zooplankter species and 23 species of littoral inverbebrates (with 3 ostracods common to both lists) were encountered; most lived at lower salinities (<30 g L−1) and none was found >60 g L−1. Dominants were mainly crustaceans and included Boeckella triarticulata and Daphnia angulata when hyposaline, and Daphniopsis queenslandensis, Moina baylyi, Diacypris spp., andMytilocypris splendida at higher salinities. Insects were generally limited to hyposaline conditions, but Micronecta sp., and Tanytarsus barbitarsis were euryhaline. Overall, the invertebrate fauna is depauperate by comparison with saline lakes elsewhere in Australia, but similar to that in other large saline lakes in the semi-arid and arid zones of central and eastern Australia. This is related to the lake’s episode nature which provides an unreliable and unpredictable habitat and therefore not encouraging speciation and also to a relatively homogenous habitat throughout the lake due to strong wind action smoothing shorelines vertically and horizontally. [pdf 112.6 kb]

document Anthropogenic salinisation of inland waters
Many inland waters are becomingmore saline fromhuman activities, particularly in semi-arid and arid regions. The causes and distribution of anthropogenic salinisation, the salinisation of freshwater lakes, rivers and streams, and increases in the salinity of large, permanent saline lakes are discussed. The impacts of anthropogenic salinisation are far-reaching, increasing, deleterious and largely irreparable. Environmental, social and environmental costs are high. Attention is drawn to the importance of anthropogenic salinisation and its impacts. The need for better recognition of the costs of salinisation and for more effective management is stressed. [pdf 651.3 kb]

document Contributions of groundwater conditions to soil and water salinization
Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or human-induced processes. Water is lost through one or any combination of four main mechanisms: evaporation, evapotranspiration, hydrolysis, and leakage between aquifers. Salinity increases from catchment divides to the valley floors and in the direction of groundwater flow. Salinization is explained by two main chemical models developed by the authors: weathering and deposition. These models are in agreement with the weathering and depositional geological processes that have formed soils and overburden in the catchments. Five soil-change processes in arid and semi-arid climates are associated with waterlogging and water. In all represented cases, groundwater is the main geological agent for transmitting, accumulating, and discharging salt. At a small catchment scale in South and Western Australia, water is lost through evapotranspiration and hydrolysis. Saline groundwater flows along the beds of the streams and is accumulated in paleochannels, which act as a salt repository, and finally discharges in lakes, where most of the saline groundwater is concentrated. In the hummocky terrains of the Northern Great Plains Region, Canada and USA, the localized recharge and discharge scenarios cause salinization to occur mainly in depressions, in conjunction with the formation of saline soils and seepages. On a regional scale within closed basins, this process can create playas or saline lakes. In the continental aquifers of the rift basins of Sudan, salinity increases along the groundwater flow path and forms a saline zone at the distal end. The saline zone in each rift forms a closed ridge, which coincides with the closed trough of the groundwater-level map. The saline body or bodies were formed by evaporation coupled with alkaline-earth carbonate precipitation and dissolution of capillary salts. [pdf 640.8 kb]

document Controlled water table management as a strategy for reducing salt loads from subsurface drainage under perennial agriculture in semi-arid Australia
Recent community based actions to ensure the sustainability of irrigation and protection of associated ecosystems in the Murrumbidgee Irrigation Area (MIA) of Australia has seen the implementation of a regional Land andWater Management Plan. This aims to improve land and water management within the irrigation area and minimise downstream impacts associated with irrigation. One of the plan objectives is to decrease current salt loads generated from subsurface drainage in perennial horticulture within the area from 20 000 tonnes/year to 17 000 tonnes/year. In order to meet such objectives Controlled Water table Management (CWM) is being investigated as a possible ‘Best Management Practice’, to reduce drainage volumes and salt loads. During 2000–2002 a trial was conducted on a 15 ha subsurface drained vineyard. This compared a traditional unmanaged subsurface drainage system with a controlled drainage system utilizing weirs to maintain water tables and changes in irrigation scheduling to maximize the potential crop use of a shallow water table. Drainage volumes, salt loads and water table elevations throughout the field were monitored to investigate the effects of controlled drainage on drain flows and salt loads. Results from the experiment showed that controlled drainage significantly reduced drainage volumes and salt loads compared to unmanaged systems. However, there were marked increases in soil salinity which will need to be carefully monitored and managed. [pdf 3.4 Mb]

document Ecological risk to aquatic systems from salinity increases
An article from Australian Journal of Botany 51, published in 2003. Written by Barry T. Hart, P.S. Lake, J. Angus Webb and Michael R. Grace of the CRC for Freshwater Ecology, Monash University. [pdf 1.1 Mb]

document Effects of increasing salinity on freshwater ecosystems in Australia
An article from Australian Journal of Botany 51, published in 2003. Written by D.L. Nielsen, M.A. Brock, G.N. Rees and D.S. Baldwin. [pdf 312.8 kb]

document Effects of saline drinking water on growth and water and feed intakes of weaner heifers
An article from the Australian Journal of Experimental Agriculture 25, published in 1985. The results of an experiment conducted by G.R. Saul and P.C. Flinn. [pdf 278.6 kb]

document Environmental threats to salt lakes and the likely status of inland saline ecosystems in 2025
Salt lakes are geographically widespread, numerous and a significant part of the world’s inland aquatic ecosystems. They are important natural assets with considerable aesthetic, cultural, economic, recreational, scientific, conservation and ecological values. Some features, notably the composition of the biota, uniquely distinguish them from other aquatic ecosystems. The paper reviews the nature of environmental impacts and their effects upon salt lakes. Its aims are two-fold: to draw attention to the extensive damage that salt lakes have now undergone, and to indicate the likely status of salt lakes in 2025. [pdf 231.6 kb]

document Groundwater–surface water interactions in a large semi-arid floodplain: implications for salinity management
Flow regulation and water diversion for irrigation have considerably impacted the exchange of surface water between the Murray River and its floodplains. However, the way in which river regulation has impacted groundwater–surface water interactions is not completely understood, especially in regards to the salinization and accompanying vegetation dieback currently occurring in many of the floodplains. Groundwater–surface water interactions were studied over a 2 year period in the riparian area of a large floodplain (Hattah–Kulkyne, Victoria) using a combination of piezometric surface monitoring and environmental tracers (Cl, υ2H, and υ18O). Despite being located in a local and regional groundwater discharge zone, the Murray River is a losing stream under low flow conditions at Hattah–Kulkyne. The discharge zone for local groundwater, regional groundwater and bank recharge is in the floodplain within ¾1 km of the river and is probably driven by high rates of transpiration by the riparian Eucalyptus camaldulensis woodland. Environmental tracers data suggest that the origin of groundwater is principally bank recharge in the riparian zone and a combination of diffuse rainfall recharge and localized floodwater recharge elsewhere in the floodplain. Although the Murray River was losing under low flows, bank discharge occurred during some flood recession periods. The way in which the water table responded to changes in river level was a function of the type of stream bank present, with point bars providing a better connection to the alluvial aquifer than the more common clay-lined banks. Understanding the spatial variability in the hydraulic connection with the river channel and in vertical recharge following inundations will be critical to design effective salinity remediation strategies for large semi-arid floodplains. [pdf 527.1 kb]

document Queensland Murray-Darling Basin Salinity Assessment Summary Report- November 2000
This is a summary report made on the November of 2000 in regards the assessment of salinity in Queensland’s Murray-Darling basin. [pdf 14.9 Mb]

document Responses of freshwater biota to rising salinity levels and implications for saline water management: a review
An article from the Australian Journal of Botany 51, published in 2003. Written by Kimberley R. James, of the Deakin University, and Belinda Cant and Tom Ryan of the Department of Sustainability and Environment. [pdf 263.5 kb]

document Saline groundwater seepage zones and their impact on soil and water resources in the Spicers Creek catchment, central west, New South Wales, Australia
Saline seepage zone development and hence dryland salinity is a major environmental problem which many arid to semiarid landscapes in Australia are experiencing. Due to the geological complexity of the regional aquifer system and the heterogeneous nature of the local groundwater system, each groundwater seepage zone in the Spicers Creek catchment, central west, New South Wales, Australia possesses different mechanisms which control its development. Saline seepage zones have formed adjacent to a fault zone, and two experimental sites were established through these groundwater discharge zones to understand geochemical processes which have led to the development of soil sodicity, gully erosion and the flushing of salts into the surface water systems. Seepage zone groundwaters contain a distinctive geochemical signature with elevated concentrations of Na, Cl, HCO3, Ca, Sr, B, As and Li. The mixing of deep saline groundwaters together with ion exchange processes lead to a distinctive seepage zone groundwater chemistry being developed. Altering the landscape features within this rural groundwater system has developed water toxicity for crops, soil sodicity leading to land degradation, and waterlogging problems. [pdf 757.0 kb]

document Salt accumulation in semi-arid floodplain soils with implications for forest health
Dieback of native Eucalyptus largiflorens forests is an increasing problem on the floodplains of the lower River Murray, southern Australia. Salinisation of floodplain soils, as a result of the changed hydrological management of the River Murray, appears to be a primary cause of the dieback. Regulation of the River Murray has reduced the frequency of large flood events by a factor of approximately three and caused groundwater levels beneath floodplains to rise. The higher water tables have resulted in increased discharge of the naturally saline groundwater in the floodplains by evapotranspiration, and the decreased incidence of large floods has reduced floodwater recharge and hence leaching of salt from floodplain soils. Use of soil physical properties for a range of floodplain soils, combined with measurements of groundwater discharge from bare and vegetated sites, suggests that the time-scale for complete soil salinisation can, at worst, be less than 20 years. Moreover, salt accumulation at most sites will continue to occur as the present flooding regime (of which there is limited scope for improvement) appears incapable of providing the leaching required to counteract accumulation. The analyses carried out here suggest that the 'critical' water table depth (below which groundwater discharge is balanced or exceeded by floodwater recharge) needs to be increased by 14 55% (the more clayey the soil, the larger the increase) to prevent salt accumulation. Failure to implement schemes which lower the water tables beneath the floodplain may, in the long term, cause serious damage to these important riparian forests. [pdf 1.3 Mb]

document Salt lakes in Australia: present problems and prognosis for the future
Australia is a land of salt lakes and despite low human population density, many lakes are adversely impacted by a range of factors. Secondary salinisation is the most pernicious force degrading lakes, especially in south-west Western Australia where up to 30% of the landscape is predicted to be affected. Mining also impinges on many salt lakes in this state, mainly through the dewatering of saline groundwater. Exploitation of groundwater for irrigation caused some lakes in Victoria, Australia, to dry, especially the significant Red Rock Complex. Global climate change will result in new water balances in endorheic lakes, with most having less water, particularly the seasonal lakes of southern Australia. This has already happened in Lake Corangamite, Victoria, but the prime reason is diversion of inflowing floodwater. Consequently, the lake has retreated and become salinised compromising its status as a Ramsar site. Various other lakes suffer from enhanced sedimentation, have introduced biota or their catchments are being disturbed to their detriment. Enlightened management should be able to maintain some important lakes in an acceptable condition, but, for most others, the future is bleak. [pdf 553.7 kb]

document Spatial and temporal variability of water salinity in an ephemeral, arid-zone river, central Australia
This study describes the spatial and temporal variability of water salinity of the Neales–Peake, an ephemeral river system in the arid Lake Eyre basin of central Australia. Saline to hypersaline waterholes occur in the lower reaches of the Neales–Peake catchment and lie downstream of subcatchments containing artesian mound springs. Flood pulses are fresh in the upper reaches of the rivers (<200 mg l1). In the salt-affected reaches, flood pulses become increasingly saline during their recession. It is hypothesized that leakage from the Great Artesian Basin deposits salt at the surface. This salt is then transported by infrequent runoff events into the main river system over long periods of time. The bank/floodplain store downstream of salt-affected catchments contains high salt concentrations, and this salt is mobilized during the flow recession when bank/floodplain storage discharges into the channel. The salinity of the recession increases as the percentage of flow derived from this storage increases. A simple conceptual model was developed for investigating the salt movement processes during flow events. The model structure for transport of water and salt in the Neales–Peake catchment generated similar spatial and temporal patterns of salt distribution in the floodplain/bank storage and water flow as observed during flow events in 2000–02. However, more field-data collection and modelling are required for improved calibration and description of salt transport and storage processes, particularly with regard to the number of stores required to represent the salt distribution in the upper zone of the soil profile. [pdf 349.1 kb]

document The impact of flooding on modelling salt transport processes to streams
The development of many of the world's arid and semi-arid regions has resulted in the salinisation of land and water resources. In these areas, soils and groundwaters are often naturally saline and any disturbance of the delicate hydrological balance results in mobilisation of the stored salt. The salt transport mechanisms are often highly complex, the understanding of which necessitates the use of computer modelling in combination with field studies. In this paper the transport of salt between groundwater and streams on the Chowilla floodplain in south-eastern Australia was modelled and compared with available field data. The large salinity contrast between the fresh stream and floodwater and the saline groundwater results in density-dependent flow behaviour, and hence necessitated the use of a variable density flow and solute transport model (SUTRA). The model was applied in cross-section over a 6.I-km-long transect across the floodplain. Time varying boundary conditions were employed at the locations of three streams on the transect to simulate the interaction between the rising and falling streams and the adjacent aquifer during and after floods. The model was used to assess the importance of overbank floods in the transport of salt to floodplain streams by carrying out simulations under various recharge scenarios. The simulations showed that the mixing of floodwater and groundwater within the bank storage adjacent to the streams could predict the observed short-term ( < 12 months) salt load recessions. In order to predict the observed long-term (12-24 months) salt load recessions, the inclusion of localised recharge during overbank floods is required, as hypothesised by previous field-based studies. [pdf 1.4 Mb]

document Understanding farmers’ monitoring of water tables for salinity management
Given the prominence of dryland salinity as a resource management problem in Australia, it might be expected that farmers would keenly monitor the levels of saline groundwater under their farms. However, many farmers choose not to monitor, in some cases even when they have previously installed bores suitable for this purpose. We investigated this apparent paradox by analysing the monitoring behaviour of a group of farmers in the Jerramungup region of southern Western Australia. The farmers are unusual in displaying a very high rate of monitoring compared with other regions, although this rate has fallen over the past decade. A range of physical, economic and social influences on monitoring behaviour are identified by statistical analysis of survey and physical data. A key finding is that farmers who are using the information from monitoring to assess salinity management strategies implemented on their farms are likely to monitor more frequently. This suggests that monitoring frequency may be driven in large part by the availability of suitable salinity management practices that can be implemented, in contrast to the view that adoption of salinity management practices may be enhanced by programs that encourage monitoring. [pdf 169.7 kb]