Numerical Modeling of Wave Reflection from Sloped Impermeable Seawalls Using the SPH Method: Case Study of Chabahar Port

In this research, a comprehensive study is performed to investigate the interaction of regular waves with the impermeable seawall of the Chabahar port. First, a MIKE 21 SW model is used to transform the deep-water wave data to the nearshore zone. Then, the interaction of waves with the seawall is simulated using a well-known numerical smoothed particle hydrodynamics model named DualSPHysics. After validating the numerical results with the experimental data, a parametric study is performed to evaluate the effects of the wave height, wave period, and the slope of the seawall on the water level fluctuations and the wave reflection coefficient. The results showed that increasing the wave height slightly decreases the reflection coefficient. Meanwhile, a direct relationship was found between the wave height and the water level fluctuations near the wall. Generally, increasing the wave period resulted in higher reflection coefficients and water level fluctuations. Both the reflection coefficient and the water level fluctuations are greatly dependent on the slope of the seawall. Steeper slopes resulted in higher reflection coefficients and lower water level fluctuations near the seawall.

High-resolution insight into the Holocene environmental history of the Burullus Lagoon in northern Nile delta, Egypt

The modern Nile delta developed in the Middle and Late Holocene, and at its most northern-central point is situated at the Burullus Lagoon, which is environmentally diverse, including salt marshes, mudflats, and sand plains, and separated from a sea by a sand barrier overtopped with high sand dunes. The lagoon has been fed since the Middle Holocene by the Sebennitic branch of the Nile and marine intrusions through the Bughaz inlet. A sediment core (BO-1) was collected at the northeastern shore of the lagoon and sampled at centennial scale resolution in order to reconstruct the development of the lagoon. The results show that an initial and limited lagoon had developed at the end of the Early Holocene, but after a dry period ca. 7.2 cal ka BP it has been progressively transformed into a marshy area, with occasional inflows of sea water. Lower water level and higher salinity of the Burullus Lagoon at 6.0–5.5 and 4.8–4.2 cal ka BP reflected droughts in the Nile catchment. Thereafter, the river reactivated in the Burullus Lagoon area, and since 2.8 cal ka BP was accompanied by occasional inflows of sea water. Since ca. 0.8 cal ka BP, increased fluvial activity occurred in this part of the Nile delta, which terminated after construction of the Aswan dams in the twentieth century.

Morphological Features of Plants on Ash Settling Ponds. Case Study

Owing to variable water conditions, chemical conditions of water or ash substrate, ash settling ponds belong to anthropogenic objects which do not easily undergo plant succession. However, there are plants exhibiting biological traits allowing colonisation of a substrate characterised by variability in terms of acidity and heavy metal content. The aim of the study was to determine differences in morphology of plants colonising spontaneous surfaces of ash settling ponds with variability moisture level. We identified also differences in morphology of the plants. Identified: Agrostis stolonifera, Atriplex patula, Juncus bufonius, Phragmites australis, Poa pratensis and Ranunculus sceleratus. The obtained results broaden the knowledge on the bioremediation of degraded areas, indicate species that inhabit the surface of ash settlers. Lower water level in ash settling pond I created more favourable conditions for growth of the aboveground parts of plants, and higher waterlevel in ash settling pond II contributed to a more intensive development of the root part of plants. Considering the generative factors and measurement values of the aboveground part of plants, the best adapted species were Juncus bufonius and Atriplex patula. Due to changing water level in ash settling ponds, the species to be monitored is Phragmites australis—most deeply colonising the surface of ash settling ponds.

Abiotic factors driving cyanobacterial biomass and composition under perennial bloom conditions in tropical latitudes

While warming and eutrophication have increased the frequency and magnitude of harmful cyanobacterial blooms globally, the scenario for many eutrophic tropical freshwaters is a perennial year-round bloom. Yet, the drivers of persistent blooms are less understood when conditions such as light, temperature, and nutrients favor cyanobacteria growth year-round, and especially in regions facing recurrent periods of drought. In order to understand the drivers of cyanobacteria dominance, we assessed the abiotic conditions related to the abundance and dominance of the two dominant bloom-forming genera Raphidiopsis and Microcystis, in six shallow, man-made lakes located in the semiarid Northeastern region of Brazil during a prolonged regional drought. Lower water level corresponded to increased phosphorous and nitrogen concentration and, consequently, phytoplankton biomass. Cyanobacterial biomass was also proportional to phosphorus concentrations during year-round blooms. Yet, the two dominant cyanobacterial genera, Raphidiopsis and Microcystis, seldom co-occurred temporally and the switch between them was driven by water transparency. Our results illustrate the effects of drought induced water level reductions on the biomass and composition of cyanobacterial blooms in tropical shallow man-made lakes. Given the ideal year-round conditions (i.e., high light and temperature), droughts may be expected to intensify the risk and multitude of problems associated with eutrophication.

Severe Historical Droughts Carved on Rock in the Yangtze

The White Crane Ridge (WCR) Rock Fish, now submerged under the backwater of the Three Gorges Reservoir in the Yangtze River, are affirmed as one of the earliest hydrologic observations ever made in any large river in the world. The usually in-water monument provides highly valuable historical records of severe droughts in the upper Yangtze over the last 1,200 years. This article updated the historical drought chronology previously developed based on the WCR inscriptions, which can be applied in assessment of extreme climatic and hydrological risks, and also made a preliminary analysis of changes of the severe drought frequency during the last thousand years in the upper Yangtze. The analysis shows that the severe droughts occurred more frequently during the Medieval Climate Anomaly (MCA), relatively less so during the Little Ice Age (LIA), and once again more often under the background of modern global warming. It was suggested that a generally warmer Euro-Asian continent during the MCA was in favor of the stronger East Asian summer monsoon, and the resulting less precipitation and more severe droughts of the Yangtze and the lower water level at the Three Gorges area on the centennial scale, and vice versa for the period of the LIA. The results would help in understanding the causes and mechanisms of the regional climate change and variability, and also in taking measures in the fields of the watershed management to cope with the long-term change in climatic and hydrologic droughts.

Dracunculiasis: water-borne anthroponosis vs. food-borne zoonosis

Dracunculiasis is the first parasitic disease set for eradication. However, recent events related to the Dracunculus medinensis epidemiology in certain African countries are apparently posing new challenges to its eradication. Two novel facts have emerged: the existence of animal reservoirs (mainly dogs but also cats and baboons), and possibly a new food-borne route of transmission by the ingestion of paratenic (frogs) or transport (fish) hosts. Therefore, instead of being exclusively a water-borne anthroponosis, dracunculiasis would also be a food-borne zoonosis. The existence of a large number of infected dogs, mainly in Chad, and the low number of infected humans, have given rise to this potential food-borne transmission. This novel route would concern not only reservoirs, but also humans. However, only animals seem to be affected. Dracunculus medinensis is on the verge of eradication due to the control measures which, classically, have been exclusively aimed at the water-borne route. Therefore, food-borne transmission is probably of secondary importance, at least in humans. In Chad, reservoirs would become infected through the water-borne route, mainly in the dry season when rivers recede, and smaller accessible ponds, with a lower water level containing the infected copepods, appear, whilst humans drink filtered water and, thus, avoid infection. The total absence of control measures aimed at dogs (or at other potential reservoirs) up until the last years, added to the stimulating reward in cash given to those who find parasitized dogs, have presumably given rise to the current dracunculiasis scenario in Chad.

Impact of water level fluctuation in the shaping of zooplankton assemblage in a shallow lake.

Shallow lakes are strongly affected by global climate changes reflected in significant parameters of ecosystem deterioration, i.e. biodiversity decrease, and water turbidity. Zooplankton research in Škrčev kut oxbow lake (Krapina River watershed, NW Croatia, Europe) was conducted during the summer of 2012 and 2013 with the aim to determine the effect of inter-annual, short-timescale changes of hydrological regime on environmental conditions, macrophytes, zooplankton and fish assemblage within an oxbow lake in the temperate region. Within one-year period the water level increased by 2 meters. This caused a significant reduction of floating-leaved macrophytes (i.e.Nuphar lutea), while turbidity, ortho-phosphate and chlorophyllaconcentrations increased. These altered ecological conditions were reflected in the shift from floating-leaved macrophytes at the lower water level to phytoplankton-dominated lake at the higher water level. Zooplankton underwent significant alteration in assemblage. The results suggest that fish preference suppressed cladocerans and enhanced the rotifer and copepod abundance. Our results indicate that even in a short-timescale zooplankton assemblage mediates in the modification of ecosystem functioning.

Controlling the Intensity of a Bathtub Vortex by Acting on the Upstream Flow

In a motor vehicle, the cowl box is a volume located at the bottom of the windshield. It collects rainwater and drains it to provide clean and dry air to the passenger compartment through the ventilation system. When rainwater is accumulated into the box, a bathtub vortex appears above the drain pipe. This vortex sucks up air into the pipe and creates an air core responsible of the decreased water drain rate in the pipe. It leads to an increased water level in the box and can cause a water overflow into the ventilation system. The behavior of this bathtub vortex has been experimentally studied using a simplified geometry representative of a real cowl box. The inlet water flow rate is controlled and a capacitive probe measures water level in the box. The flow has been studied using Particle Image Velocimetry to measure velocity field around the vortex. The flow pattern is described using these data. Due to geometry and inlet conditions, the upstream flow forces the vortex counter-clockwise. It is also responsible for a shift of the vortex axis from the drain axis. In this configuration, the upstream flow is strongly asymmetric and feeds the vortex using less than half the width of the box. Based on these observations, a device has been tested in order to reduce the vortex intensity and consequently the water level. Resulting velocity fields show a better distribution of the upstream flow. The vortex intensity is decreased up to 55% and the water level up to 53%. Despite there is still a vortex with an air core, the water level is therefore significantly reduced. These results are particularly interesting for the cowl box design: if this device can guarantee a lower water level, the cowl box depth can be reduced and space can be saved.

Experimental Study on Flow Conditions of Jiaogang Ship Lock during Sluice Gate Hoist

The physical model of Jiaogang Ship Lock is established. Through model test, the flow condition in lock chamber and approach channel is studied. The results indicate when the upstream water level keeps high and the water level difference between upstream and downstream is less than 0.5 meter, the main flow oscillates less during spring tide flux and reflux in the flood year. When the upper water level is 0.96 m and during spring tide flux and reflux in the flood year, the flow is from downstream to upstream and the flow is smooth. When the upper water level is greater than lower water level, the sluice gate hoist condition is tidal range less than 0.3m in tide flux and less than 0.4m in tide reflux. Under the critical water level conditions, the Jiaogang Ship Lock sluice gate can be hoisted safely.