Academic literature on the topic 'Salinisation'

Mestrado em Biologia Aplicada<br>As global climate patterns change, so will freshwater availability. Specially, salinisation of freshwater costal ecosystem is a major point of concern; either by surface flooding or by groundwater intrusions of seawater. This may be potentiated by the decrease of freshwater availability provoked by longer drought periods, evaporation, and increased freshwater extraction (for example for agriculture and other human uses). According, the present work aimed at evaluating how freshwater organisms responded to an increase in salinity. To achieve this main objective two specific goals were delineated: (i) to compare the toxicity of seawater with a surrogate (NaCl), commonly used in laboratory toxicity assays, to two standard freshwater species, and (ii) to assess if an association exist between resistance to chemical contamination and to increased salinity; since many populations, predicted to experience future increased salinity, are presently exposed to chemical contamination. To accomplish the first objective the sensitivity of the green algae Pseudokirchneriella subcapitata (Korshikov) F. Hindák and of the cladoceran Daphnia magna Straus to NaCl and to natural seawater was evaluated. Growth rate for P. subcapitata, and mortality, time to release the first brood, body size, total reproduction, and intrinsic rate of natural increase for D. magna, were monitored after exposing these species to two series of solutions with an increasing gradient of salinity. One series of solutions was established with a natural seawater sample and the other with NaCl dissolved artificial media. To address the second objective, four cloned lineages of Daphnia longispina O.F. Müller, exhibiting different sensitivities to lethal levels of copper, were exposed to a gradient of lethal and sublethal levels of salinity, established with the salt NaCl. The same endpoins described for D. magna were also monitored for D. longispina. The obtained results showed that NaCl exerted a higher toxicity to P. subcapitata (LOEC of 5.9mS/cm and 9.6mS/cm, respectively for NaCl and seawater) and to D. magna (LC50,48h of 9.88mS/cm and 11.32mS/cm; and EC50 for total reproduction of 8.9mS/cm and 10.4mS/cm, respectively for NaCl and seawater) than the natural seawater. These data suggest that the use of NaCl as a surrogate for seawater to predict, in laboratory, the effects of seawater intrusion in freshwater is a protective approach as it simulates a “Worst Case Scenario” of exposure. An association between resistance to copper and to NaCl was not observed for the tested cloned lineages of D. longispina (r < 0.92 and p > 0.08), though the two clonal lineages most resistant to copper also exhibited the highest sensitivity to sublethal levels of NaCl (determined as the EC20 for total reproduction). Finally, obtained data demonstrated that D. longispina was more sensitive to increased salinity (LC50,48h of 2.85g/L to 2.48g/L or, conductivity values of LC50,48h of 5.50mS/cm to LC50,48h= 4.57mS/cm which correspond respectively to the highest and lowest recorded values in these assays) than the standard species (D. magna), highlighting the importance of using autochthonous species for the ecological risk assessment of secondary salinisation.<br>À medida que os padrões climáticos se alteram também a disponibilidade de água doce se irá alterar. Como tal, a salinização de ecossistemas costeiros, principalmente os dulçaquicolas, torna-se um ponto de preocupação fundamental. Quer devido ao aumento de intrusões de água do mar por inundação ou por intrusões salinas através dos lençóis freáticos, quer devido à diminuição de entrada de água doce, provocada por períodos mais prolongados de seca, evaporação e aumento do uso de água para actividades antropogénicas. De acordo com o exposto, o presente trabalho pretendeu avaliar as respostas de organismos dulçaquicolas a alterações provocadas pelo aumento de salinidade. Para atingir este objectivo principal foram delineados dois objectivos específicos: (i) comparar a toxicidade de água do mar com a do sal NaCl, comummente usado em laboratório como substituto de água do mar e (ii) averiguar uma possível correlação entre a resistência a contaminação química (cobre) e a aumento de salinidade; uma vez que muitas das populações que se prevê virem a ser afectadas por salinização estão, presentemente, já expostas a contaminação química. Para abordar o primeiro objectivo, a alga verde Pseudokirchneriella subcapitata (Korshikov) F. Hindák e o cladócero Daphnia magna Straus foram expostos a dois gradientes crescentes de salinidade estabelecidos com água do mar natural e com NaCl dissolvido num meio artificial.. No ensaio com a alga verde unicelular foi avaliada a inibição do crescimento; no ensaio com D. magna foram avaliados os seguintes parâmetros: mortalidade, tempo decorrido até libertar a primeira ninhada, comprimento corporal, reprodução total, taxa de crescimento intrínseco. Para atingir o segundo objectivo, foram seleccionadas quatro linhagens do cladócero Daphnia longispina O.F Müller com sensibilidades diferentes a níveis letais de cobre. As quatro linhagens foram expostas a um gradiente de concentrações, letais e sub-letais, de NaCl. Neste ensaio foram analisados os mesmo parâmetros descritos anteriormente para o ensaio com D. magna. Os resultados demonstram que o sal NaCl apresentou maior toxicidade do que a água do mar natural, quer para P. subcapitata (LOEC de 5.9mS/cm e de 9.6mS/cm, respectivamente para NaCl e água do mar), quer para D. magna (LC50,48h de 9.88mS/cm e LC50,48h= 11.32mS/cm; e EC50, para reprodução total, de 8.9mS/cm e 10.4mS/cm, respectivamente para NaCl e água do mar). Estes dados sugerem que o uso de NaCl, em laboratório, como um substituto de água do mar deve ser considerado como uma abordagem protectora, uma vez que simula um cenário de maior toxicidade. Não foi observada uma associação significativa entre maior resistência a cobre e a NaCl nas linhagens de D. longispina testadas (r < 0.92 and p ≥ 0.08), apesar de as duas linhagens mais resistentes a cobre apresentarem as maiores sensibilidades a níveis subletais (para reprodução total) de NaCl. Finalmente, os dados obtidos demonstram que D. longispina é mais sensível ao aumento de salinidade (o intervalo de valores de LC50,48h calculados foi de 2.85g/l a 2.48g/l de NaCl, correspondente a valores de conductividade de 5.50mS/cm e 4.57mS/cm, respectivamente) que a espécie padrão (D. magna), salientando a importância do uso de espécies autóctones na avaliação de risco ecológico em situações de intrusões salinas.

Dryland salinity is increasing in the upper catchments of central and northern New South Wales, Australia. Consequently, salts may be exported downstream, which could adversely affect cotton irrigated-farming systems. In order to assess the potential threat of salinity a simple salt balance model based on progressively saline water (i.e., ECiw 0.4, 1.5, 4.0 and 9.0 dS/m) was used to simulate the potential impact of salinisation due to the farming systems. The study was carried out in the lower Namoi valley of northern New South Wales, Australia. A comparison has been made of the various non-linear techniques (indicator kriging, multiple indicator kriging and disjunctive kriging) to determine an optimal simulation method for the risk assessment. The simulation results indicate that potential salinisation due to application of the water currently used for irrigation (ECiw) is minimal and may not pose any problems to sustainability of irrigated agriculture. The same results were obtained by simulation based on irrigation using slightly more saline water (ECiw 1.4 dS/m). However, simulations based on irrigation using water of even lower quality (ECiw of 4 and 9.0 dS/m), shows potential high salinisation, which will require management inputs for sustainable cropping systems, especially legumes and wheat, which are used extensively in rotation with cotton. Disjunctive kriging was the best simulation method, as it produced fewer misclassifications in comparison with multiple-indicator kriging and indicator kriging. This study thus demonstrates that we can predict the salinity risk due to application of irrigation water of lower quality than that of the current water used. In addition, the results suggest here problems of excessive deep drainage and inefficient use of water might be a problem. The second part of this thesis deals with soil information required at the field scale for management practices particularly in areas where deep drainage is large. Unfortunately, traditional methods of soil inventory at the field level involve the design and adoption of sampling regimes and laboratory analysis that are time-consuming and costly. Because of this more often than not only limited data are collected. In areas where soil salinity is prevalent, detailed quantitative information for determining its cause is required to prescribe management solutions. This part deals with the description of a Mobile Electromagnetic Sensing System (MESS) and its application in an irrigated-cotton field suspected of exhibiting soil salinity. The field is within the study area of part one of this thesis-located about 2 km south west of Wee Waa. The EM38 and EM31 (ECa) data provide information, which was used in deciding where soil sample sites could be located in the field. The ECa data measured by the EM38 instrument was highly correlated with the effective cation exchange capacity. This relationship can be explained by soil mineralogy. Using different soil chemical properties (i.e. ESP and Ca/Mg ratio) a detailed transect study was undertaken to measure soil salinity adjoining the water storage. It is concluded that the most appropriate management option to remediation of the problem would be to excavate the soil directly beneath the storage floor where leakage is suspected. It is recommended that the dam not be enlarged from its current size owing to the unfavourable soil mineralogy (i.e. kaolin/illite) located in the area where it is located.

Dryland salinity is increasing in the upper catchments of central and northern New South Wales, Australia. Consequently, salts may be exported downstream, which could adversely affect cotton irrigated-farming systems. In order to assess the potential threat of salinity a simple salt balance model based on progressively saline water (i.e., ECiw 0.4, 1.5, 4.0 and 9.0 dS/m) was used to simulate the potential impact of salinisation due to the farming systems. The study was carried out in the lower Namoi valley of northern New South Wales, Australia. A comparison has been made of the various non-linear techniques (indicator kriging, multiple indicator kriging and disjunctive kriging) to determine an optimal simulation method for the risk assessment. The simulation results indicate that potential salinisation due to application of the water currently used for irrigation (ECiw) is minimal and may not pose any problems to sustainability of irrigated agriculture. The same results were obtained by simulation based on irrigation using slightly more saline water (ECiw 1.4 dS/m). However, simulations based on irrigation using water of even lower quality (ECiw of 4 and 9.0 dS/m), shows potential high salinisation, which will require management inputs for sustainable cropping systems, especially legumes and wheat, which are used extensively in rotation with cotton. Disjunctive kriging was the best simulation method, as it produced fewer misclassifications in comparison with multiple-indicator kriging and indicator kriging. This study thus demonstrates that we can predict the salinity risk due to application of irrigation water of lower quality than that of the current water used. In addition, the results suggest here problems of excessive deep drainage and inefficient use of water might be a problem. The second part of this thesis deals with soil information required at the field scale for management practices particularly in areas where deep drainage is large. Unfortunately, traditional methods of soil inventory at the field level involve the design and adoption of sampling regimes and laboratory analysis that are time-consuming and costly. Because of this more often than not only limited data are collected. In areas where soil salinity is prevalent, detailed quantitative information for determining its cause is required to prescribe management solutions. This part deals with the description of a Mobile Electromagnetic Sensing System (MESS) and its application in an irrigated-cotton field suspected of exhibiting soil salinity. The field is within the study area of part one of this thesis-located about 2 km south west of Wee Waa. The EM38 and EM31 (ECa) data provide information, which was used in deciding where soil sample sites could be located in the field. The ECa data measured by the EM38 instrument was highly correlated with the effective cation exchange capacity. This relationship can be explained by soil mineralogy. Using different soil chemical properties (i.e. ESP and Ca/Mg ratio) a detailed transect study was undertaken to measure soil salinity adjoining the water storage. It is concluded that the most appropriate management option to remediation of the problem would be to excavate the soil directly beneath the storage floor where leakage is suspected. It is recommended that the dam not be enlarged from its current size owing to the unfavourable soil mineralogy (i.e. kaolin/illite) located in the area where it is located.

[Truncated abstract] Land clearing is known to increase runoff, and in many dryland landscapes is also associated with rising saline watertables, causing increased stream salinity and degrading riparian vegetation. The limited understanding of how river morphology responds to these changes and the potential for vegetation-based strategies to offer river management options under these conditions, has prompted this research. In southwestern Australia the severity of salinity and recent nature of land clearing provides an appropriate setting to investigate river response. A data-based, multidisciplinary methodology was applied to determine how land clearing and landscape salinisation has altered landscape sensitivity through changes in erosive potential, system connectivity and material threshold mechanisms, and how these affect patterns of river response. The study investigated the responses of morphologically similar reaches across fifty two study sites in the Kent River and Dalyup River catchments, in the south coastal rivers region of Western Australia. Land clearing was found to have significantly altered the hydrologic regime and erosive potential in both frequency and magnitude, with flow becoming more perennial, and increased annual discharge, flood peaks and bankfull flow frequency. While sediment transport rates have also increased since land clearing, they remain low on a global scale. Human response to a reduced rainfall regime and related water security pressures has caused large hillslope areas to be decoupled from the main channels by bank and farm dam construction, and have reduced downstream transmission of change. ... By contrast, steeper-sloped mid-catchment areas with minimal vegetation degradation caused by salinity are associated with higher erosive potential. A more erosive response is observed in these reaches where floodplains have been cleared for agricultural purposes. A conceptual model of vegetation growth across the salinity gradient observed in the study catchments was developed, and applied to selected river styles to assess the potential that vegetation-based strategies offer for river management. This work identifies the unsuitability of river restoration strategies, but the potential for river restoration or remediation in a saline landscape. Hydraulic modelling demonstrated that river rehabilitation strategies such as improving the vegetation condition of the riparian buffer using native or commercial species on areas elevated above saline flow can stabilise reaches. For river styles in wide and flat valleys, there is limited potential for vegetation-based river rehabilitation under the current salinity gradient. Field observation and modelling suggest that river remediation may offer geomorphic management options in salt-affected reaches through channelisation to lower watertables, and further research on this is warranted. This work found a consistent response for river styles across the two study catchments. Based on the understanding of river response and the potential for vegetation-based river management for each style, this research offers a regional-scale tool for river management in a saline landscape.

Les aquiferes cotiers, part non negligeable des ressources en eau des bassins sedimentaires en france, ont subi des changements de gradients hydrauliques et de proprietes hydrodynamiques, en reponse aux periodes de decharge/recharge dues aux variations du niveau marin et/ou aux forcages anthropiques. Cette etude a pour objectif principal la comprehension des conditions de recharge et de decharge a l'origine des eaux salees reconnues sur trois sites : les aquiferes du dogger des cotes de la manche (caen) et de l'atlantique (marais poitevin), ainsi que l'aquifere des sables astiens (cap d'agde). Pour les trois sites, les eaux douces recentes sont marquees par une anthropisation des aires de recharge. Le long d'une ligne d'ecoulement, les signatures geochimiques dependent de la nature des formations aquiferes et relevent des interactions eau-roche. Les temps de residence des eaux douces evoluent de l'actuel (site atlantique) a la limite de la methode du 1 4c (site de la manche). Les eaux de l'aquifere des sables astiens montrent une gamme d'ages holocene, determinee par le 1 4c et le 2 2 6ra. De l'actuel a 3 ka, les ages 1 4c et 2 2 6ra sont identiques. Au dela, les ecarts observes peuvent etre associes a une sous-estimation de la production de 2 2 6ra in-situ, mais plus vraisemblablement, a l'effet tampon- 1 4c lors de l'equilibration isotopique avec la matrice. D'origine marine, la signature des eaux salees reconnues sur les trois sites a ete modifiee par interaction avec des horizons tourbeux, par echange cationique, ou par apport de carbone d'origine profonde. Ces processus de salinisation sont lies a un debordement marin en plaine ou a une drainance d'eau carbo-gazeuse provenant d'un aquifere profond. Les intrusions marines affectant des sites de l'atlantique et de la manche ont pu etre associees a la transgression flandrienne (respectivement 8 ka et 4,8-10,8 ka b. P. ). Pour les sables astiens, le temps ecoule depuis le melange profond eau-co 2 a pu etre estime a 0,5-3 ka.

The thesis looks at landscape evolution and salinisation in the Bamganie-Meredith region of Victoria. The importance of reducing waterlogging is stressed if successful land management is to be achieved.<br>Master of Applied Science