Causes, impacts, and sustainability issues of dryland salinity on wetlands in Australia SWES 574 W. J. Ward 12/09/2003

Mining and Agriculture Anthropogenic Salinisation Diverted inflows for irrigation and other uses Excessive clearance of natural, deep rooted vegetation from catchments Discharge of saline agricultural wastewater Rising saline groundwater Mining and discharge of brine waters  Salinity rising in: Mono Lake, CA., Pyramid Lake, NV., Aral Sea, Asia, Qinghai Hu, China, Lake Qarum, Egypt, Lake Corangamite, AUS. and rivers Syr, Amu darya, Asia, Blackwood, AUS.  Dryland salinities result from:

Anthropogenic Salinisation (cont.)  Salinisation common in semi-arid regions of annual rainfall of mm  % of all irrigated land has been effected by salinisation  Potential to cause irreversible damage to arid land rivers and wetlands  In Australia lost agricultural production is $ 50 mil/yr U.S. and degradation of infrastructure is an additional $ 90 mil/yr. U. S.  Vegetation death is caused by toxic levels of bicarbonate, magnesium, sulphate, sodium, and chloride  Loss of species and species diversity  Waters become unusable for irrigation or drinking

Copper Lode Gold Bauxite Tin Nickel Uranium Figure 1 – Known Mineral Resources

Removal of native vegetation causes increased recharge to groundwater Water table rises with increased groundwater mobilization Low Permeability layer Saline Seeps Dry land Crops and Grazing Hydraulic Pressure and upward groundwater movements in aquifers Saline soil develops where water table rises to less than 2 meters from surface Saline groundwater in drains Saline lake size increases as water table rises Figure 2. Clearing deep rooted vegetation leads to salinity of rivers and lakes

CEC = total amount of exchangeable cations that can be held by a given mass of soil

Exchangeable Ca / Na Cation Experiment Saturate Arizona White House Bt horizon clay with NaCl Cations Removed Cl ions by washing Mix clay with sand for permeable layer Flow solution of CaCl 2 through clay/sand Remove excess Ca cations and Cl ions by washing Extract Ca cations with LaMotte Extraction Solution Precipitate Ca cations with LaMotte Sodium Oxalate Compare sample precipitate with LaMotte sample strip

RESULTS: Visually compare test tube results with PPM chart   Background CaNa Exchanged 130 mg/L Ca Na Exchanged in Sat. Ca

Figure 3. Dryland Salinity Hazard  Tree clearing in upper part of catchment  Winter rains with low evapotranspiration  Fractured rock deep groundwater aquifer  Hydraulic head beneath clay floor  Kaolinite, illite, and semectite in debris- flow allows cation-exchange releasing sodium  Clays decrease hydraulic conductivity under saturated conditions Australian rising groundwater salinity – sequence of events & dryland salinity hazard mapping using GIS

Summary Early mining timber use and early settlement and agriculture land clearing degraded long term sustainability Increased recharge creates valley area groundwater discharge through clay debris flow. Discharge cation exchange causes increased salinity of surface waters negatively impacting lakes and wetlands

Summary (cont.) Column experiment simulated the cation exchange between Ca & Na in high CEC clays Cation exchange occurring in Yass River Catchment, New South Wales, Australia causing rising salinity in rivers, lakes, and wetlands Mapping salinity and remediation to prevent excess infiltration is key to further damage

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