Sources of surface water for the Soncor ecosystem,Salar de Atacama basin,northern Chile

Abstract

The Salar de Atacama is located in the most arid desert in the world. Despite its extreme conditions, it has many ecosystems of high ecological value. The Soncor ecosystem, a sequence of lagoons, is the most important environment of the region as it acts as the centre for the breeding of the Andean Flamingo. This salt flat also contains significant mining deposits and is an important water source for the region. Freshwater and brine—enriched in lithium and potassium—are being pumped from the aquifers near to the Soncor ecosystem, which has so far not been greatly affected by this groundwater extraction. However, there is a potential risk that future anthropogenic effects may disturb this fragile environment. The objective of this study is to determine the origin of the water sources of the Soncor ecosystem so as to adequately manage its water resources. Three hypotheses previously proposed in the technical literature were investigated in order to determine proactive actions to protect this fragile ecosystem. The study utilized classic hydrogeological techniques, such as the construction of stratigraphic profiles, piezometric maps and stream gauging, combined with less-common isotopic techniques, such as the ⁸⁷Sr/⁸⁶Sr ratio. The results confirmed the hypothesis that the origins of the water sources are associated with groundwater inputs coming from the east side of the salt flat, in the north of the basin.

Editor Z.W. Kundzewicz; Associate editor M. Acreman

Citation Ortiz, C., Aravena, R., Briones, E., Suárez, F., Tore, C., and Muñoz, J.F., 2014. Sources of surface water for the Soncor ecosystem, Salar de Atacama basin, northern Chile. Hydrological Sciences Journal, 59 (2), 336–350.     

Evaluation of secondary compression of sands and silts from CPTU

The estimate of secondary compression behaviour of sandy and silty deposits is not routinely taken into account in the classical settlement calculation, due to its generally limited contribution to the total amount of strains. However, such soils exhibit a non-negligible time-dependent behaviour and the prediction of their long-term response may sometimes be important.

This paper explores the capability of the piezocone test as an effective tool to estimate the one-dimensional secondary compression characteristics of sands and silts. The approach is mainly based on the observation that frictional response essentially governs both secondary compression of granular soils and cone resistance, hence it seems reasonable to establish a valid correlation among them.

The study uses part of the field data assembled over the last years at the Treporti Test Site (Venice, Italy), within an extensive research project aimed at analysing the stress-strain-time response of the predominantly silty sediments forming the Venetian lagoon subsoil.

Empirical, site-specific correlations for estimating the secondary compression coefficient from cone resistance are proposed. The regression analyses indicate that the estimate is slightly improved if the cone resistance-based correlations include a variable accounting for the different pore pressure response associated to the drainage conditions around the advancing cone.     

河北七里海外海岸沙丘群成因新探

七里海有中国第一大潟湖之称,多数学者认为七里海外的海岸沙丘群是在滨外沙坝的基础上发育形成的。研究认为,七里海外的海岸沙丘群是在末次冰期时期风成沙丘群的基础上演化形成的继承性沙丘综合体。七里海也不是科学意义上的潟湖,它没有形成海岸沙坝这一潟湖形成的过程,其前身是晚更新世末期由风暴活动形成的风蚀洼地。应加强七里海外海岸沙丘群的形成、发育类型及演化过程的研究,从多角度探究七里海外海岸沙丘群的演化机理和发育趋势。     

江苏小庙洪牡蛎礁的地貌特征及演化

江苏岸外的小庙洪牡蛎礁在海岸地貌学上是一稀有的生物沉积体。这种位于蚀、淤交替岸段潮间带、古礁体和活体共存的牡蛎礁体是我国所仅见。现场观察了牡蛎礁体的地貌特征,并使用GPS和全站仪进行了主要礁体分布与高程的测量,表明礁区地貌面不是一个水平面,相差可达2m以上。礁体顶高主要分布在两个高程上,一是与平均潮位相当,二是比前者低约30cm,略高于小潮平均低潮位。礁体起伏面高出礁坪面多在0.5—1.5m。小庙洪牡蛎礁正处于退化状态,除物理因素造成的侵蚀外,化学溶蚀及人类活动也是侵蚀退化的主要因素。对于礁区内部的礁体,其退化过程为连片礁→环礁→带礁→斑礁→礁坪的顺序。礁体沉积体有三种:原生礁体、与原生礁体脱离的礁块以及已离开原生地的松散堆积体。浪蚀礁坪分布在礁体的迎浪面上,而溶蚀礁坪则分布在礁体密集区。在礁体稀疏区,则覆盖约20—30cm厚的粉沙或淤泥,形成次生的潮坪。     

鄂尔多斯盆地下奥陶统马家沟组障壁潟湖沉积相模式及有利储层分布规律

依据鄂尔多斯盆地古构造古地理背景、古水动力以及古气候条件,结合单井沉积相分析建立了马家沟组障壁潟湖沉积相模式,该模式分三个阶段即与海侵期相对应的以灰岩沉积为主的障壁潟湖沉积阶段(阶段Ⅰ)、与海退相对应的以灰岩夹蒸发岩沉积为主的障壁咸化潟湖沉积阶段(阶段Ⅱ)和与低海平面期对应的以膏岩盐沉积为主的障壁膏盐湖沉积阶段(阶段Ⅲ...     

Applicability of piezocone and dilatometer to characterize the soils of the Venice Lagoon

The effectiveness of two geotechnical investigation tools—the piezocone and the dilatometer—to characterize the soils forming the shallowest deposits of the upper quaternary basin of the Venice lagoon soil is examined in this study. For this purpose, the results of a comprehensive site and laboratory investigation carried out recently over a small lagoon area—the Malamocco Test Site—are used to evaluate the applicability of the most widely used charts or correlative equations to characterize soil profile and estimate the main geotechnical properties of these soils, when applied to the interpretation of CPTU and DMT results. The particular interest of this site—apart from its unquestionable historical relevance—is the presence, apparently without any regular pattern in depth and site, of a predominantly silty fraction combined with clay and/or sand, thus forming an erratic interbedding of various types of sediments. This case represents therefore the opposite condition of that which has been normally utilized in the past to calibrate the two devices, namely the presence of particularly homogeneous natural deposits or artificially sedimented homogeneous layers of sand or clay. The Malamocco Test Site may therefore be considered as test benchmark for the applicability of the two devices to characterize highly heterogeneous silty deposits.     

华南港湾海岸的地貌特征

本文根据作者参加华南海岸和港口调查研究的体会,对华南现代海岸的形成条件和港湾海岸的地貌特点进行分析。     

Factors affecting offspring growth and daily nest survival rates in the coastal breeding Western Reef Heron (Egretta gularis) in the Persian Gulf

Offspring growth and nest survival of waterbirds are important and prominent characteristics of their life history. Nestling growth and daily survival rates of the Western Reef Heron Egretta gularis were studied in Hara Biosphere Reserve, Persian Gulf, Iran. Growth parameters were determined in relation to both age ranking of each nestling within a brood and the brood size using data from known‐age nestlings. Nesting success was modeled based on the information‐theoretic approach implemented by the program MARK to assess the effects of clutch initiation date, nest size and location on daily survival rates of nests. Mean daily growth rate of body mass was 18.06 ± 6.22 g during the first 2 weeks of age and was independent of brood size but was greater in nestlings hatching earlier within the brood. Wing and tarsus growth rate was influenced by both brood size and nestling rank within the brood, but culmen growth was independent of both factors. Earlier hatched nestlings grew faster than those hatched later. Growth of all morphometric parameters followed the Logistic growth curve model except for wing chord, which fitted the Gompertz growth model. Nest size and nest height above the ground were the most important predictors of nest survival (ω_i = 0.79 and ω_i = 0.69, respectively), with survival among Western Reef Heron nests improving as the nest size and nest height increased. This study shows the importance of temporal and spatial variables for breeding ecology of a common but little‐known breeding heron in coastal areas of Persian Gulf.     

Variability of nutrients and phytoplankton primary production in a shallow macrotidal coastal ecosystem (Arcachon Bay,France)

Seasonal and spatial variations of phytoplankton primary production were studied using a high frequency sampling strategy in the external (ENW) and internal (INW) part of Arcachon Bay, during 2002 and 2003. In order to better assess the availability of nutrients and their relationship with phytoplankton primary production, nutrient variability was studied in relation to environmental conditions and phytoplankton production. During winter, when primary production rates were the lowest, nutrient concentrations were maximal but did not show excessive levels compared to highly urbanised areas. Seasonal and spatial variations of nutrient concentrations (especially DIN-nitrate + nitrite + ammonium- and Si) were largely influenced by Leyre River loads coupled with high tidal exchange with the Atlantic Ocean creating a nutrient gradient between the INW and ENW. By February, diatom growth leads to an early severe nutrient depletion in the entire bay. Examination of nutrient ratios showed that the potential limiting nutrient during spring was P in 2003, and Si in 2002. During summer 2003, N and Si concentrations reached their lowest values, and nutrient ratios revealed a N-deficient environment, more pronounced in the INW. The high Si:N ratios during this period might be explained by (1) important N-uptake by all autotroph communities and (2) benthic-pelagic coupling with high Si regeneration. This study shows that nutrient levels in Arcachon Bay seem to play an important role in the control of phytoplankton primary production rates during the productive period and explain their spatial, seasonal and inter-annual variability. Our estimates of annual integrated phytoplankton primary production (103 g C m⁻² y⁻¹) place this bay within the low to moderate phytoplankton primary production systems.