Amount Of River Discharge Research Articles

Analysis of the Distribution and Seasonal Variability of the South China Sea Water Masses Based on the K-means Cluster Method

Influenced by local mixing and coastal runoff, water masses in the South China Sea degenerate significantly. The K-means algorithm is used to classify the water masses based on WOD13 temperature and salinity observations from 1966 to 2013 because its principle is consistent with the definition of a shallow water mass. The numbers and initial centers of the water masses are determined using functions of in-cluster distance and density values. The result shows that there are ten water masses in the South China Sea. In combination with the T-S scatter diagram, the properties of the South China Sea water masses were analyzed, including their distribution, the seasonal variability, and the degeneration processes. The temperatures of water masses were higher in summer and lower in winter, with the amplitudes of variation gradually reduced from the surface to the bottom. The seasonal variation in salinity of the surface water masses was high in winter and low in summer, which mainly depends on the amount of river discharge and precipitation. The subsurface water masses were strongly affected by water from the Pacific Ocean; thus, the seasonal variability of these water masses is weak, especially for the intermediate water mass that characterized by prominent low salinity. The water mass formed by the Kuroshio water invading the South China Sea has insignificant seasonal variations in temperature and salinity. The properties and seasonal variabilities of the water masses derived from the K-means algorithm are in agreement with the existing conclusions, suggesting that the improved K-means algorithm is efficient and accurate in the shallow water mass division.

The calculation of flushing time for the upper Pasur River Estuary, Bangladesh

Estimation of estuarine flushing time, a time required to transport of pollutants or any other properties from estuaries to the coast, is very important for its resource management. In this study, we estimated flushing time (T) of the upper Pasur River Estuary (UPRE) for understanding the water quality condition in the dry and wet seasons. High-resolution salinity data were collected from the PRE at high water in the dry and wet seasons in 2014 and 2019. Flushing time was calculated using the freshwater fraction method (FFM) as well as e-folding flushing time scales was estimated empirically using the salinity (non-reactive conservative) and monthly river discharge data. System flushing during the dry season was thirteen times weaker than flushing during the wet season owing to decreasing river discharge by nearly 94%. In addition, the daily exchange volume was decreased by eight times during the dry season than during the wet season. As a consequence, the conditions of the UPRE are more dynamic during the wet season due to receiving huge amount of river discharge. During the dry season, only the e-folding time scales showed higher values in the salinity maximum zone (salt plug area). This implied that the e-folding time scale is an empirical approach and was able to encompass the tidal dispersion process whereas the FFM was unable to include that process. As the PRE is a macrotidal estuary, the tide assists to flush dissolved substances from the UPRE to the coast during the dry season having negligible river discharge. In addition, there was no significant variation in water quality parameter between the salt plug area (SP) and downstream of salt plug area (DSP) during the dry season. In order to have more accuracy, a three-dimensional hydrodynamic model would be useful to compute estuarine time scales precisely.

Testing thermodynamics method for salt intrusion during infrequent astronomical event

Knowledge of the processes governing salt intrusion in estuaries is important since it influences the eco-environment of estuaries as well as its water resource potential in many ways. The aim of this paper is to test the effectiveness of the new 1-D thermodynamic salt intrusion equation proposed by Zhang and Savenije (i.e., is an extreme power theory for the mixing of saline sea water and fresh river water in estuaries); and existing salt intrusion model (i.e., Van der Burgh method) at two previously unsurveyed estuaries in India and Morocco. To successfully perform the analysis using the 1-D models, real time data is required. Field measurements during infrequent astronomical event were recorded along the estuaries (31/01/2018 for Ashtamudi estuary (India); and during 31/01/2018 for Bouregreg estuary (Morocco)). Shape (geometry) and salinity analyses were performed on each of the estuaries. The results obtained show good agreement between the simulated and observed salinity distribution in the estuaries with high R 2 values. Finally, by utilizing the new predictive equation, we can estimate the minimum amount of river discharge needed, and the maximum allowable depth for dredging, to prevent saline water intruding further into the areas studied. Thus, the simple and effective approach presented in this study can describe the current state of salt intrusion in India and Morocco estuaries, and be used for future development.

ANALISA PENGENDALIAN BANJIR AKIBAT PELUAPAN DEBIT ALIRAN DENGAN PERKUATAN TEBING TIPE SHEET PILE “Studi Kasus Sungai Batang Lumpo Kabupaten Pesisir Selatan”

Flooding ia caused by the increased volume of water’s volume in the river or lake so that water is out of its natural limits. The flooding is mostly caused by inadequate river capacity to accommodate river discharge. The amount of river discharge at the time of flood is caused by the increasing amount of surface runoff from the rains that fall in the catchment area. Based on the preliminary survey conducted, it was found that the frequency of flooding in the Batang Lumpo river area is 2-3 times a year with a height ranging from 0.5 to 1.5 meters from the soil surface with the duration of inundation ranges from 4 to 6 hours. Areas affected by flooding ranging from the area of Nagari Taratak Tengah Lumpo Kecamatan IV Jurai down to the downstream river at Nagari Pasar Baru Kecamatan Bayang. By the result of the analysis obtained flood discharge using Rational method Q 100 years = 237, 26 m³ / dt, high h = 2.7 m, the high value of W = 1.16 m length Sheet Pile in flood condition = 4.14 m, Maximum Moment Mmax = 6, 31 tm and sheet pile length in dry condition = 3.16 m, Mmax Moment = 7,125 t.m.

Seasonal changes in abiotic environmental conditions in the Busan coastal region (South Korea) due to the Nakdong River in 2013 and effect of these changes on phytoplankton communities

We studied phytoplankton community structure at 25 stations in the Busan coastal region (South Korea), including the Nakdong River estuary, during four seasons in 2013. Together with the observational study, we conducted an experimental study to assess the effects of nutrient enrichment on phytoplankton community structure over seasonal succession. Over the study period, abiotic environmental factors, such as water temperature, salinity, and nutrient concentrations, in the Busan coastal region were associated with the amount of discharge from the Nakdong River; salinity and nutrient levels varied depending on the amount of river discharge, and the water temperature in winter near the Nakdong River estuary was significantly lower due to the increase in river discharge compared to other regions. However, the water temperature in offshore stations was relatively high owing to the introduction of the Tsushima Warm Current (TWC). During winter and summer, diatoms were the predominant taxa; the primary dominant species were Stephanodiscus hantzschii (winter), Leptocylindrus danicus (spring), and small diatoms (summer). In summer, blooms of the dinoflagellate Cochlodinium polykrikoides occurred at several stations near the Nakdong River mouth and several offshore stations, and small diatoms were abundant at the sampling stations. In autumn, Cryptomonas spp. were dominant (>60%) at most sample stations. To investigate the response of phytoplankton communities to nutrient loading, bioassay experiments with phytoplankton samples collected from five sampling stations during four seasons were conducted through the addition of inorganic nutrients: nitrate (+N; 20 µM), phosphate (+P; 2 µM phosphate), and nitrate and phosphate (+NP; at the same concentrations). The +NP treatment exhibited the highest growth enhancement of phytoplankton in most samples. In addition, depending on the NP ratio and phytoplankton community structure, there was a distinct response of phytoplankton to nutrient loading. These results imply that phytoplankton can grow under conditions of pulsed nutrient loading, irrespective of season, but there may be seasonal difference in response of phytoplankton communities in the Busan coastal region.

Decrease in growth increment of Populus euphratica upon defoliation by Lepidopteran larvae in a Central-Asian floodplain forest

Populus euphratica is a constitutive tree species of the mostly monospecific forests along Central-Asian rivers. In the hyper-arid climate along the Tarim River, Xinjiang, NW China, these trees are phreatophytes with continuous access to the groundwater. Those poplar stands are often moderately to completely defoliated by Lepidopteran larvae in spring. In a P. euphratica stand at the middle reaches of the Tarim River, which grew close to the river and to the water table, we tested whether severe defoliation significantly reduces the trees' radial stem increment and their production of above-ground wood biomass even at ample water supply by the river.Tree-ring analyses and allometric regressions revealed a drastic decrease in radial stem increment and annual above-ground wood production upon complete defoliation even in a period of ample water supply, which otherwise would have allowed maximum productivity. The loss of above-ground production by herbivory amounted to approximately 44% relative to the high production rate of the year before complete defoliation. During the recent decade, however, only the amount of river discharge – but not the estimated intensity of defoliation – was (marginally) significantly correlated with the stem increment. We conclude that in P. euphratica forests growing close to the river and to the groundwater, tree growth is mainly related to the amount of river discharge, but can be significantly reduced in years with complete defoliation. Therefore, defoliation events should be considered in assessing the productivity of these riparian forests.

Spatiotemporal variation of Gaoping River plume observed by Formosat-2 high resolution imagery

River plumes play an important role in river–ocean boundary systems, where suspended and dissolved materials are exchanged between the land and ocean. Optical images acquired from space-borne platforms have been widely employed to study the spatiotemporal variations of major river plumes around the world. Gaoping River (GPR), which flows in a small basin with steep slopes, has a high sediment load with dynamic spatiotemporal variations. This research employed a total of 41 images of the GPR estuary acquired by Formosat-2 from 2005 to 2008 to study the spatiotemporal variations of the related river plume, as well as the influences of tidal, precipitation, river discharge, wind, current, and extreme weather events. All images were processed to be geo-referenced and radiometric-calibrated images using the Formosat-2 Auto Image Processing System. Three different water types, including plume core, plume/shelf water and offshore water, were classified by the supervised maximum likelihood classification method. The results show that the size of the plume core is directly correlated with the amount of river discharge and precipitation, while the direction of the plume on- and off-shore is controlled by the flood and ebb tides, respectively. A notable feature of the frontal patterns in the region of plume/shelf waters in GPR mouth region is that the angle between the sea surface wind direction and sea surface current direction is less than 90°. According to the observations made after four major typhoon and storm events, GPR plume expanded to as large as four times its normal size, and this condition lasted for up to 18days. These results may be applied to the other regions that are similar to GPR.

Satellite-measured temporal and spatial variability of the Tokachi River plume

River plumes have important effects on marine ecosystems. Variation in the extent and dispersal of river plumes is often associated with river discharge, wind characteristics and ocean circulation. The objectives of this study were to identify the Tokachi River plume by satellite, determine its relationship with river discharge and clarify its temporal and spatial dynamics. SeaWiFS multispectral satellite data (normalized water-leaving radiance: n L w) with 1.1 km spatial resolution were used to determine the spatial and temporal variability of the plume during 1998–2002. Supervised maximum likelihood classification using six channels of n L w at 412, 443, 490, 510, 555 and 670 nm with each band's spectral signature statistic was used to define classes of surface water and to estimate the plume area. Supervised maximum likelihood classification separated three to four classes of coastal water based on optical characteristics as a result of wind stress events. The satellite-observed plume area was correlated with the amount of river discharge from April to October. The plume distribution patterns were influenced by wind direction and magnitude, the occurrences of a near-shore eddy field and surface currents. Empirical orthogonal function (EOF) was used to express the spatial and temporal variability of the plume using anomalies of n L w(555) monthly averaged images. The first mode (44% of variance) showed the turbid plume distribution resulting from re-suspension by strong wind mixing along the coast during winter. This mode also showed the plume was distributed along-shelf direction in spring to early autumn. The second mode (17% of variance) showed spring pattern across-shelf direction. EOF analysis also explained the interannual variability of the plume signature, which might have been affected by the flow of the Oyashio Current and the occurrence of a near-shore eddy field.

Watershed management in the Dinder National Park, Sudan

A major objective of the study was to survey and map the drainage system of the park which is crucial to sound management and maintenance of the habitat. Landsat satellite data of multispectral scanner (MSS), thematic mapper (TM) and aerial photographs were the main sources of information. Visual image interpretation and field surveys were the methods employed to analyse and map the drainage patterns. The drainage system of the park includes the rivers Dinder and Rahad, their tributaries and mayas (wet meadows). Mayas are a special feature of the drainage system, straddling low-lying basins, river meanders and oxbow lakes. They are the major source of water and green fodder during the dry season (November-June). The spectrum runs from young productive wet mayas to old non-productive dry ones. During the past 2 decades and due to the decrease in the amount of river discharge and rainfall, coupled with repeated fires, the catchment areas of mayas have deteriorated drastically causing many of them to silt up to almost complete dryness. Perennial grasses, for example, have been substituted by annuals. The water and food supply available to wildlife has thus decreased greatly. The study assessed the present condition of the mayas and suggested possible means for improvement and restoring the natural storage capacities of some mayas.