Showing papers on "Saline water published in 2013"

Transient groundwater dynamics in a coastal aquifer: The effects of tides, the lunar cycle, and the beach profile

Abstract: [1] Detailed field measurements are combined with a numerical modeling to characterize the groundwater dynamics beneath the discharge zone at Waquoit Bay, Massachusetts. Groundwater salinity values revealed a saline circulation cell that overlaid the discharging freshwater and grew and disappeared with the lunar cycle. The cell was initiated by a greater bay water infiltration during the new moon when high tides overtopped the mean high-tide mark, flooding the flatter beach berm and inundating a larger area of the beach. The dynamics of this cell were further characterized by a tracer test and by constructing a density-dependent flow model constrained to salinity and head data. The numerical model captured the growing and diminishing behavior of the circulation cell and provided the estimates of freshwater and saline water fluxes and travel times. Furthermore, the model enabled quantification of the relationship between the characteristics of the observed tidal cycle (maximum, minimum, and mean tidal elevations) and the different components of the groundwater circulation (freshwater discharge, intertidal saline cycling, and deep saline cycling). We found that (1) recharge to the intertidal saline cell is largely controlled by the high-tide elevation; (2) freshwater discharge is positively correlated to the low-tide elevation, whereas deep saline discharge from below the discharging freshwater is negatively correlated to the low-tide elevation. So, when the low-tide elevation is relatively high, more freshwater discharges and less deep saltwater discharges. In contrast when low tides are very low, less freshwater discharges and more deep salt water discharges; (3) offshore inflow of saline water is largely insensitive to tides and the lunar cycle.

Alleviation of salt stress-induced adverse effects on maize plants by exogenous application of indoleacetic acid (IAA) and inorganic nutrients - A field trial

Abstract: The effects of indoleacetic acid (IAA) and inorganic nutrients (K and P) on some physiological parameters and kernel yield of maize (Zea mays L.) cultivar DK 647 F1 were investigated in two parallel experiments conducted in the same growth season in a saline field. Sodium chloride equivalent to 100 mM was added to the irrigation water and saline water applied to the field using a drip irrigation system. Indoleacetic acid was applied as foliar spray. Potassium and P were applied to the soil at the sowing time as monopotassium phosphate at 200 kg ha -1 . Salinity significantly reduced shoot dry mass, cob yield, total kernel yield, weight of 1000 kernels, chlorophylls “a” and “b” and relative water content in the maize plants, but increased proline accumulation, activities of the key antioxidant enzymes superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7), catalase (CAT; EC. 1.11.1.6) and polyphenol oxidase (PPO; 1.10.3.1), and electrolyte leakage. However, application of K and P or foliar spray of IAA mitigated the adverse effects of salinity on maize plants. The most promising effect of IAA or K and P on alleviation of salt stress on maize was found when they were applied in combination. Leaf sodium (Na + ) concentration increased substantially, but leaf K + , Ca 2+ and P concentrations decreased markedly in the salt stressed maize plants. However, exogenous application of nutrients, IAA, or their combination considerably reduced Na + concentration and significantly improved K + , Ca 2+ , and P levels in the salt stressed maize plants. The exogenously applied inorganic nutrient- or auxin-induced growth promotion in maize plants was found to be associated with increased photosynthetic pigment concentration and leaf Na + /K + ratio, reduced membrane permeability, and altered activities of

Factors controlling mechanisms of groundwater salinization and hydrogeochemical processes in the Quaternary aquifer of the Eastern Nile Delta, Egypt

Abstract: In this study, combining interpretations of conservative dissolved ions and environmental isotopes in water were used to investigate the main factors and mechanisms controlling groundwater salinization and hydrogeochemical processes in the Eastern Nile Delta, Egypt. Hydrogeochemical and isotopic study has been carried out for 61 water samples from the study area. Total dissolved solid (TDS) contents of groundwater are highly variable rising along flowpath from the south (410 mg/L) to the north (14,784 mg/L), implying significant deterioration and salinization of groundwater. Based on TDS and ionic ratios, groundwater samples were classified into three groups. In low-saline groups, water chemistry is greatly influenced by cation exchange, mineral dissolution/precipitation, anthropogenic pollutants and mixing with surface water. Whilst, in high-saline groups, water chemistry is affected by salt-water intrusion, reverse cation exchange and evaporation. The chemical constituents originating from saline water sources, reverse ion exchange and mineral dissolution are successfully differentiated using ionic delta and saturation index approaches. The δ18O–δ2H relationship plots on a typical evaporation line, suggesting potential evaporation of the recharging water prior to infiltration. Isotope evidence concludes that the groundwater have been considerably formed by mixing between depleted meteoric water recharged under different climatic conditions and recently infiltrating enriched surface water and excess of irrigation water. The δ18O data in conjunction with chloride concentrations provide firm evidence for impact of dissolution of marine-origin evaporite deposits, during past geologic periods, on groundwater salinity in the northern region. Moreover, the relation between 14C activities and Cl− concentration confirms this hypothesis.

A GIS Cost Model to Assess the Availability of Freshwater, Seawater, and Saline Groundwater for Algal Biofuel Production in the United States

Abstract: A key advantage of using microalgae for biofuel production is the ability of some algal strains to thrive in waters unsuitable for conventional crop irrigation such as saline groundwater or seawater. Nonetheless, the availability of sustainable water supplies will provide significant challenges for scale-up and development of algal biofuels. We conduct a partial techno-economic assessment based on the availability of freshwater, saline groundwater, and seawater for use in open pond algae cultivation systems. We explore water issues through GIS-based models of algae biofuel production, freshwater supply (constrained to less than 5% of mean annual flow per watershed) and costs, and cost-distance models for supplying seawater and saline groundwater. We estimate that, combined, these resources can support 9.46 × 10(7) m(3) yr(-1) (25 billion gallons yr(-1)) of renewable biodiesel production in the coterminous United States. Achievement of larger targets requires the utilization of less water efficient sites and relatively expensive saline waters. Despite the addition of freshwater supply constraints and saline water resources, the geographic conclusions are similar to our previous results. Freshwater availability and saline water delivery costs are most favorable for the coast of the Gulf of Mexico and Florida peninsula, where evaporation relative to precipitation is moderate. As a whole, the barren and scrub lands of the southwestern U.S. have limited freshwater supplies, and large net evaporation rates greatly increase the cost of saline alternatives due to the added makeup water required to maintain pond salinity. However, this and similar analyses are particularly sensitive to knowledge gaps in algae growth/lipid production performance and the proportion of freshwater resources available, key topics for future investigation.

Hydrochemistry of groundwater in a coastal region of Cuddalore district, Tamilnadu, India: implication for quality assessment

Abstract: A hydrogeochemical investigation was conducted in a coastal region of Cuddalore district to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. The geology of the study area comprises of sandstone, clay, alluvium, and laterite soils of Tertiary and Quaternary age. A total of 18 groundwater samples were analyzed for 14 different water quality parameters and the result indicates higher concentrations of ions like Cl (3,509 mg/l), Na (3,123 mg/l), and HCO3 (998 mg/l) when compared with WHO, BIS, and ISI standards. A positive correlation (r2 = 0.82) was observed between Na and Cl, indicating its sources from salt water intrusion. Three factors were extracted with a total variance of 64% which indicates the sources of salinization, cation exchange, and anthropogenic impact to the groundwater. The Piper trilinear diagram indicates both Na–Cl and mixed Na–HCO3–Cl-type, indicating that groundwater was strongly affected by anthropogenic activities. The plot of (Ca + Mg)/(K + Na) indicates evidences of cation exchange and salt water intrusion. The (Ca–0.33*HCO3)/ SO4 plot indicates salt water intrusion for elevated SO4 levels rather than gypsum dissolution. The spatial distribution of total dissolved solid indicates the saline water encroachment along the SW part of the study area. As per sodium adsorption ratio (SAR), 50% of the samples with 10 SAR indicates that water is unsuitable for irrigation purposes. The residual sodium carbonate classification indicates that 50% of the samples fall in safe and 50% of the samples fall in bad zones and prolonged usage of this water will affect the crop yield. The Chloro Alkaline Index of water indicates disequilibrium due to a higher ratio of Cl > Na–K, indicating the influence of salt water intrusion. The Permeability Index of the groundwater indicates that the groundwater from the study area is moderate to good for irrigation purposes.

Effects of salt stress and rhizobial inoculation on growth and nitrogen fixation of three peanut cultivars

Abstract: Increasing soil salinity represents a major constraint for agriculture in arid and semi-arid lands, where mineral nitrogen (N) deficiency is also a frequent characteristic of soils. Biological N fixation by legumes may constitute a sustainable alternative to chemical fertilisation in salinity-affected areas, provided that adapted cultivars and inoculants are available. Here, the performance of three peanut cultivars nodulated with two different rhizobial strains that differ in their salt tolerance was evaluated under moderately saline water irrigation and compared with that of N-fertilised plants. Shoot weight was used as an indicator of yield. Under non-saline conditions, higher yields were obtained using N fertilisation rather than inoculation for all the varieties tested. However, under salt stress, the yield of inoculated plants became comparable to that of N-fertilised plants, with minor differences depending on the peanut cultivar and rhizobial strain. Our results indicate that N fixation might represent an economical, competitive and environmentally friendly choice with respect to mineral N fertilisation for peanut cultivation under moderate saline conditions.

Effects of Increasing Salinity Stress and Decreasing Water Availability on Ecophysiological Traits of Quinoa (Chenopodium quinoa Willd.) Grown in a Mediterranean‐Type Agroecosystem

Abstract: Quinoa is a native Andean crop for domestic consumption and market sale, widely investigated due to its nutritional composition and gluten-free seeds. Leaf water potential (Ψleaf) and its components and stomatal conductance (gs) of quinoa, cultivar Titicaca, were investigated in Southern Italy, in field trials (2009 and 2010). This alternative crop was subjected to irrigation treatments, with the restitution of 100 %, 50 % and 25 % of the water necessary to replenish field capacity, with well water (100 W, 50 W, 25 W) and saline water (100 WS, 50 WS, 25 WS) with an electrical conductivity (ECw) of 22 dS m−1. As water and salt stress developed and Ψleaf decreased, the leaf osmotic potential (Ψπ) declined (below −2.05 MPa) to maintain turgor. Stomatal conductance decreased with the reduction in Ψleaf (with a steep drop at Ψleaf between −0.8 and 1.2 MPa) and Ψπ (with a steep drop at Ψπ between −1.2 and −1.4 MPa). Salt and drought stress, in both years, did not affect markedly the relationship between water potential components, RWC and gs. Leaf water potentials and gs were inversely related to water limitation and soil salinity experimentally imposed, showing exponential (Ψleaf and turgor pressure, Ψp, vs. gs) or linear (Ψleaf and Ψp vs. SWC) functions. At the end of the experiment, salt-irrigated plants showed a severe drop in Ψleaf (below −2 MPa), resulting in stomatal closure through interactive effects of soil water availability and salt excess to control the loss of turgor in leaves. The effects of salinity and drought resulted in strict dependencies between RWC and water potential components, showing that regulating cellular water deficit and volume is a powerful mechanism for conserving cellular hydration under stress, resulting in osmotic adjustment at turgor loss. The extent of osmotic adjustment associated with drought was not reflected in Ψπ at full turgor. As soil was drying, the association between Ψleaf and SWC reflected the ability of quinoa to explore soil volume to continue extracting available water from the soil. However, leaf ABA content did not vary under concomitant salinity and drought stress conditions in 2009, while differing between 100 W and 100 WS in 2010. Quinoa showed good resistance to water and salt stress through stomatal responses and osmotic adjustments that played a role in the maintenance of a leaf turgor favourable to plant growth and preserved crop yield in cropping systems similar to those of Southern Italy.

Evidence of discharging saline formation water to the Athabasca River in the oil sands mining region, northern Alberta

Abstract: This paper summarizes various lines of evidence, including new geophysical and geochemical surveys indicating the discharge of naturally occurring saline formation water from Cretaceous and Devonian formations to the Athabasca River downstream of Fort McMurray — an active oil sands extraction area. The following features are indicative of saline water discharge: (i) the hydrogeological setting of the reach which is situated near the western, up-dip, and subcropping, edge of the Western Canada Sedimentary Basin; (ii) springs and seepage along area rivers and tributaries that have been observed and reported in previous studies; and (iii) a significant increase in dissolved solids in the river, particularly chloride, occurring in a downstream direction from Fort McMurray. Further evidence of the saline groundwater discharge was obtained from electromagnetic surveys conducted along a 125 km reach from the Clearwater River to the Firebag River. This technique was used to map the distribution of saline water in...

Investigation of soil and water salinity, its effect on crop production and adaptation strategy

Abstract: Bangladesh is a deltaic country with total area of 147,570 km2. The major part (80%) of the country consists of alluvial sediments deposited by the river Ganges, Brahmaputra, Tista, Jamuna, Meghna and their tributaries. The coastal region covers almost 29,000 sq. km or about 20% of the country. Moreover, the coastal areas of Bangladesh cover more than 30% of the cultivable lands of the country. About 53% of the coastal areas are affected by salinity. Agricultural land use in these areas is very poor, which is much lower than a country’s average cropping intensity. Salinity causes unfavorable environment and hydrological situation that restrict the normal crop production throughout the year. The factors which contribute significantly to the development of saline soil are, tidal flooding during wet season (June to October), direct inundation by saline water, and upward or lateral movement of saline ground water during dry season (November to May). The severity of salinity problem in Bangladesh increases with the desiccation of the soil. It affects crops depending on degree of salinity at the critical stages of growth, which reduces yield and in severe cases total yield is lost. Therefore, it is very important to investigate the present scenario of soil and water affected by salinity on crop production of the study area. It is found from the study area named south-western zone of Bangladesh (selected eight sites of seven Upazila under greater Khulna district) that salinity level increased in April to May and decreased in October to November in every year. It has effect on crop yield in dry season due to increased salinity level. If Ganges water supply has increased in dry season, it reduces the salinity effect in crop production in Khulna. Rainfall also reduces the surfaces soil salinity. Key words: Salinity, coastal region, cultivable lands, cropping intensity, salinity adaptability.

Osmosis During Low Salinity Water Flooding

Abstract: Several research groups have shown that injection of low saline water may yield an Enhanced Oil Recovery (EOR). The mechanisms underlying this “low salinity effect” are, however, still unclear. We believe that osmosis has been overlooked as a possible mechanism for the observed EOR effect. Osmosis is bound to occur in an oil/water/rock system when injecting low salinity water as the system is full of an excellent semi-permeable membrane, namely the oil itself. Hence we believe that this topic deserves more attention. In the present work oil droplets were observed to move under the influence of an osmotic gradient in a simple visualization experiment. The experimental setup consisted of two oil droplets in a ~1 mm diameter glass tube with salt water between them and distilled water on the outside. For a porous rock medium it is proposed that such osmotic gradients relocate oil by expanding an otherwise inaccessible aqueous phase.

Quantification of groundwater–seawater interaction in a coastal sandy aquifer system: a study from Panama, Sri Lanka

Abstract: The Panama coastal aquifer system is an important water resource in the southeast coast of Sri Lanka that provides adequate supplies of water for agriculture and domestic uses. One of the biggest threats to these fragile aquifers is the sea water intrusion. In this study, recharging mechanism and geochemical evaluation of groundwater in the coastal sandy aquifer of Panama were evaluated using chemical and stable isotope techniques. Thirty groundwater samples were collected and analyzed for their major ion concentrations and stable isotope ratios of oxygen (18O/16O) and hydrogen (D/H). All studied samples showed a ranking of major anions in the order Cl− > HCO 3 − > SO 4 2− > N-NO3 − while cations showed a decreasing order of abundance with Na+ > Ca2+ > Mg2+ > K+. Dominant groundwater hydrogeochemical types were Na–Cl and mixed Ca–Mg–Cl. Results of saturation index calculations indicate that the investigated groundwater body was mostly saturated with respect to calcite, dolomite and gypsum. In addition, stable isotope and geochemical data suggest that fresh groundwater in the aquifer is recharged mainly by local precipitation with slight modification from evaporation and saline water intrusions. Isotope data suggest that mixing of salt water with freshwater occurs in aquifers which are located towards the lagoon. Since the communities in the study area depend entirely on groundwater, an understanding of the hydrogeochemical characteristics of the aquifer system is extremely important for the better water resource management in the region.

Distribution and dynamics of soil water and salt under different drip irrigation regimes in northwest China

Abstract: A 2-year experiment was carried out to investigate the effects of different drip irrigation regimes on distribution and dynamics of soil water and salt in north Xinjiang, China. Five treatments—F7 (0.24 dS m−1 + Once every 7 days), B7 (4.68 dS m−1 + Once every 7 days), S7 (7.42 dS m−1 + Once every 7 days), F10 (0.24 dS m−1 + Once every 10 days) and F3 (0.24 dS m−1 + Once every 3 days)—were designed. For all treatments, additional 150-mm fresh water was applied on 10th November in 2009 (winter irrigation) to leach the accumulated salt. The results revealed that irrigation frequency and water quality had significant effects on the spatial distribution and change of soil water content, soil salt and the crop water consumption rate, but had a limited impact on the seasonal accumulative water consumption, and the cotton yield decreased with the decrease in irrigation frequency and water quality on the whole. During the cotton growing season, results showed that the salt mainly accumulated in the 0- to 60-cm soil layer, while the soil salt in 60- to 100-cm layer changed slightly, indicating that the drip irrigation could not leach the soil salt out of the root zone under the irrigation regimes. Therefore, salt leaching was necessary to maintain the soil water–salt balance and to prevent excessive salt accumulation in the root zone. After the 150-mm winter irrigation and subsequent thawing, soil salts were leached into the deeper layers (below 60 cm), and the soil salt content (SSC) (EC1:5) in root zone in the next year was about 0.2 dS m−1. Moreover, compared to 2009 season, the SSC within the root zone did not increase even the EC of the irrigation water was up to 7.42 dS m−1. Additionally, it is important to note that the results were concluded based on the data of the 2-year experiment; further studies are need to optimize winter irrigation amount and assess the sustainability of saline water irrigation since long-term utilization of saline water may lead to soil degradation.

Distribution and dynamics of soil water and salt under different drip irrigation regimes in northwest China

Abstract: A 2-year experiment was carried out to inves- tigate the effects of different drip irrigation regimes on distribution and dynamics of soil water and salt in north Xinjiang, China Five treatments—F7 (024 dS m -1 ? Once every 7 days), B7 (468 dS m -1 ? Once every 7 days), S7 (742 dS m -1 ? Once every 7 days), F10 (024 dS m -1 ? Once every 10 days) and F3 (024 dS m -1 ? Once every 3 days)—were designed For all treatments, additional 150-mm fresh water was applied on 10th November in 2009 (winter irrigation) to leach the accu- mulated salt The results revealed that irrigation frequency and water quality had significant effects on the spatial dis- tribution and change of soil water content, soil salt and the crop water consumption rate, but had a limited impact on the seasonal accumulative water consumption, and the cotton yield decreased with the decrease in irrigation frequency and water quality on the whole During the cotton growing season, results showed that the salt mainly accumulated in the 0- to 60-cm soil layer, while the soil salt in 60- to 100-cm layer changed slightly, indicating that the drip irri- gation could not leach the soil salt out of the root zone under the irrigation regimes Therefore, salt leaching was neces- sary to maintain the soil water-salt balance and to prevent excessive salt accumulation in the root zone After the 150-mm winter irrigation and subsequent thawing, soil salts were leached into the deeper layers (below 60 cm), and the soil salt content (SSC) (EC1:5) in root zone in the next year was about 02 dS m -1 Moreover, compared to 2009 season, the SSC within the root zone did not increase even the EC of the irrigation water was up to 742 dS m -1 Additionally, it is important to note that the results were concluded based on the data of the 2-year experiment; further studies are need to optimize winter irrigation amount and assess the sustain- ability of saline water irrigation since long-term utilization of saline water may lead to soil degradation

Modeling the effects of saline water use in wheat-cultivated lands using the UNSATCHEM model

Abstract: Waters of poor quality are often used to irrigate crops in arid and semiarid regions, including the Fars Province of southwest Iran. The UNSATCHEM model was first calibrated and validated using field data that were collected to evaluate the use of saline water for the wheat crop. The calibrated and validated model was then employed to study different aspects of the salinization process and the impact of rainfall. The effects of irrigation water quality on the salinization process were evaluated using model simulations, in which irrigation waters of different salinity were used. The salinization process under different practices of conjunctive water use was also studied using simulations. Different practices were evaluated and ranked on the basis of temporal changes in root-zone salinity, which were compared with respect to the sensitivity of wheat to salinity. This ranking was then verified using published field studies evaluating wheat yield data for different practices of conjunctive water use. Next, the effects of the water application rate on the soil salt balance were studied using the UNSATCHEM simulations. The salt balance was affected by the quantity of applied irrigation water and precipitation/dissolution reactions. The results suggested that the less irrigation water is used, the more salts (calcite and gypsum) precipitate from the soil solution. Finally, the model was used to evaluate how the electrical conductivity of irrigation water affects the wheat production while taking into account annual rainfall and its distribution throughout the year. The maximum salinity of the irrigation water supply, which can be safely used in the long term (33 years) without impairing the wheat production, was determined to be 6 dS m−1. Rainfall distribution also plays a major role in determining seasonal soil salinity of the root zone. Winter-concentrated rainfall is more effective in reducing salinity than a similar amount of rainfall distributed throughout autumn, winter, and spring seasons.

Emergência, crescimento e produção da mamoneira sob estresse salino e adubação nitrogenada

Abstract: The use of saline water in agriculture is becoming a reality in many regions of the world, given the increased demand for fresh water, both for irrigated agriculture, as well as for urban and industrial supply. In this context, the aim of this research was to evaluate the effect of different salinity levels in irrigation water, associated with amounts of nitrogen fertilizer, on the emergence, growth and yield of the castor bean, cv. BRS Energia, in an experiment where plants were maintained in lysimeters under field conditions, at the CCTA / UFCG. A randomised block design in a 5 x 5 factorial with three replications was used to study the effects of five levels of electrical conductivity of the irrigation water (0.4, 1.4, 2.4, 3.4 and 4.4 dS m-1) associated with five levels of nitrogen fertilizer (50, 75, 100, 125 and 150% of the dose recommended for testing in pots). The salinity of the irrigation water from 0.4 dS m-1 affects negatively and in a linear manner the percentage of emergence (PE), the emergence speed index (IVE), plant height (AP), the stem diameter (DC), the shoot dry-weight (FSPA) and root dry-weight (FSRaiz) and the seed mass of the primary raceme (MSemRP), whereas increasing levels of nitrogen caused an increase in DC, FSPA and FSRaiz. The application of increasing doses of N reduced the effect of salinity on the DC and FSRaiz of the castor bean cv. BRS Energia.

The temporal and spatial variability of the Yellow Sea Cold Water Mass in the southeastern Yellow Sea, 2009–2011

Abstract: The Yellow Sea Cold Water Mass (YSCWM) is one of the important water mass in the Yellow Sea (YS). It is distributed in the lower layer in the Yellow Sea central trough with the temperature less than 10°C and the salinity lower than 33.0. To understand the variability of the YSCWM, the hydrographic data obtained in April and August during 2009–2011 are analyzed in the southeastern Yellow Sea. In August 2011, relatively warm and saline water compared with that in 2009 and 2010 was detected in the lower layer in the Yellow Sea central area. Although the typhoon passed before the cruise, the salinity in the Yellow Sea central trough is much higher than the previous season. It means that the saline event cannot be explained by the typhoon but only by the intrusion of saline water during the previous winter. In April 2011, actually, warm and saline water (T >10°C, S >34) was observed in the deepest water depth of the southeastern area of the Yellow Sea. The wind data show that the northerly wind in 2011 winter is stronger than in 2009 and 2010 winter season. The strong northerly wind can trigger the intrusion of warm and saline Yellow Sea Warm Current. Therefore, it is proposed that the strong northerly wind in winter season leads to the intrusion of the Yellow Sea Warm Current into the Yellow Sea central trough and influenced a variability of the YSCW Min summer.

Delineating shallow saline groundwater zones from Southern India using geophysical indicators

Abstract: A geophysical survey was conducted over an industrial belt encompassing 80 functional leather factories in Southern India. These factories discharge untreated effluents which pollute shallow groundwater where electrical conductivity (EC) value had a wide range between 545 and 26,600 μS/cm (mean, 3, 901 μS/cm). The ranges of Na+ and Cl− ions were from 46 to 4,850 mg/L (mean, 348 mg/L) and 25 to 10,390 mg/L (mean, 1,079 mg/L), respectively. Geoelectrical layer parameters of 37 vertical electrical soundings were analyzed to demarcate fresh and saline water zones. However, the analysis not did lead to a unique resolution of saline and fresh waters. It was difficult to assign a definitive value to the aquifer resistivity of any area. Thus, geophysical indicators, namely longitudinal unit conductance (S), transverse unit resistance (T), and average longitudinal resistivity (R s), were calculated for identifying fresh and saline waters. Spatial distributions of S, T, and R s reflected widely varying ranges for the saline and fresh water zones. Further, the empirical relation of formation factor (F) was established from pore-water resistivity and aquifer resistivity for fresh and saline aquifers, which may be used to estimate local EC values from the aquifer resistivity, where well water is not available.

The Australian Cotton Industry and four decades of deep drainage research: a review

Abstract: The Australian cotton industry and governments have funded research into the deep-drainage component of the soil–water balance for several decades. Cotton is dominantly grown in the northern Murray–Darling and Fitzroy Basins, using furrow irrigation on cracking clays. Previously, it was held that furrow irrigation on cracking clays was inherently efficient and there was little deep drainage. This has been shown to be simplistic and generally incorrect. This paper reviews global and northern Australian deep-drainage studies in irrigation, generally at point- or paddock-scale, and the consequences of deep drainage. For furrow-irrigated fields in Australia, key findings are as follows. (i) Deep drainage varies considerably depending on soil properties and irrigation management, and is not necessarily ‘very small’. Historically, values of 100–250 mm year–1 were typical, with 3–900 mm year–1 observed, until water shortage in the 2000s and continued research and extension focussed attention on water-use efficiency (WUE). (ii) More recently, values of 50–100 mm year–1 have been observed, with no deep drainage in drier years; these levels are lower than global values. (iii) Optimisation (flow rate, field length, cut-off time) of furrow irrigation can at least halve deep drainage. (iv) Cotton is grown on soils with a wide range in texture, sodicity and structure. (v) Deep drainage is moderately to strongly related to total rainfall plus irrigation, as it is globally. (vi) A leaching fraction, to avoid salt build-up in the soil profile, is only needed for irrigation where more saline water is used. Drainage from rainfall often provides an adequate leaching fraction. (vii) Near-saturated conditions occur for at least 2–6 m under irrigated fields, whereas profiles are dry under native vegetation in the same landscapes. (viii) Deep drainage leachate is typically saline and not a source of good quality groundwater recharge. Large losses of nitrate also occur in deep drainage. The consequences of deep drainage for groundwater and salinity are different where underlying groundwater can be used for pumping (fresh water, high yield; e.g. Condamine alluvia) and where it cannot (saline water or low yield; e.g. Border Rivers alluvia). Continuing improvements in WUE are needed to ensure long-term sustainability of irrigated cropping industries. Globally there is great potential for increased production using existing water supplies, given deep drainage of 10–25% of water delivered to fields and WUE of <50%. Future research priorities are to further characterise water movement through the unsaturated zone and the consequences of deep drainage.

Vertical variation of oxygen isotope in Bay of Bengal and its relationships with water masses

Abstract: [1] We present here, for the first time, comprehensive depth specific (near surface to 1800 m) oxygen isotope (δ18O) data set of 175 water samples collected from 22 different locations in the Bay of Bengal (BoB) during July–August 2009 and December–January 2012–2013. The study is aimed to constrain the water mass parameters using oxygen isotope and salinity. Four water masses are identified on the basis of temperature-salinity relationship: (a) Bay of Bengal Water (BoBW; 0–50 m), (b) Mixed Zone (MZ; 60–120 m), (c) Indonesian Throughflow (ITF; 200–500 m), and (d) Indian Ocean Deep Water (IDW; 600–1800 m). Our study shows: (1) δ18O-salinity correlation (slope = 0.15 ± 0.01; intercept = −4.58 ± 0.24; r2 = 0.89; n = 54) for the BoBW is found to be consistent with surface BoB water reported earlier, (2) relatively lower correlation (r2 = 0.24; n = 47) in underlying mixed zone suggesting mixing of various water masses, (3) significant linear correlation between δ18O and salinity in IDW (r2 = 0.70) indicating depleted less saline water from southern hemisphere spread up to 18°N, and (4) vertical profiles at various sampling locations showing a continuous enrichment of δ18O (0.6–0.8‰) within top 60–100 m irrespective of their proximity to coastline. In conjunction with a sharp decrease in Δ14C data below the same depth zone (60–100 m) as reported earlier, we suggest the δ18O value reaches to its acme at a zone of mixing between younger BoBW and relatively older ITF. This preliminary study indicates oxygen isotope and salinity together can be used to identify different water masses in the BoB.