Main Drainage Canal Research Articles

Visual inspection results and evaluation of Akhtala tailing safety based on tailing management facility safety methodology

Relevance. Mining sector is one of the leading branches of the industry in Armenia. Therefore, effective government regulation of the sector based on a sound legal basis is a necessity. Accidents at tailing management facilities are posing a high risk to people and environment especially in their near vicinity and often have a transboundary impact. The tailing management facility safety methodology elaborated under the auspices of the German Environmental Agency is an efficient tool for quick assessment of the technical condition of the tailing management facilities. Aim. To present the results of application of the tailing management facility methodology in Armenia, which was applied to the operated Nahatak tailing management facility of the Akhtala Ore Dressing Combine (Lori region, Armenia). Objects. Tailing management facility methodology was applied to the operated tailing management facility Nahatak of the Akhtala Ore Dressing Combine, for which all documentation was checked. Enrichment wastes were stored at the tailing management facility during processing copper ore from the Shamlug mine and polymetals from the Akhtala mine. The main visual inspection was carried out in three parts of the tailing management facility: main dam, drainage canal and secondary dam. Special attention was drawn to main dam conditions. The video recorded by a drone was used to explore the dam bottom-line. Methods. The tailing management facility methodology includes the following elements: the method of evaluation of Tailings Hazard Index; the tailing management facility checklists including the questionnaire for visual and documentation inspection, the evaluation matrix for the tailing management facility safety level; the measures catalogue for taking actions to improve tailing management facility safety. The questions of the each tailing management facility checklist are stated in a way to encompass the minimum set of the requirements, critical for tailing management facility safety, which allows evaluating the tailing management facility conditions. Questions in all groups of the checklist are sorted by the tailing management facility lifecycle and each subsection contains relevant questions applied to a specific stage (design, construction, operation, re-cultivation, closure). Application of the tailing management facility checklist is supported by a measures catalogue with short-, medium- and long-term safety measures. Results. The tailing management facility methodology was used/tested for the operated tailing management facility in Armenia for the first time. Тhe main problems of the Nahatak tailing management facility were identified and analyzed, and appropriate recommendations were provided based on them. Based on the obtained results it can be concluded that the main problems are related to the drainage system and the management of water flows, some parts of the primary dam that require restoration, as well as the improvement of monitoring systems. At the same time the experience of application of the tailing management facility methodology in Armenia, allowed improving this methodology and making it the most effective working tool for quick and efficient visual inspection of tailing management facilities and for thorough inspection of relevant documentations. The user-friendly tailing management facility safety methodology (with questionnaires of visual and documentation checking) is an efficient tool for quick assessment of the technical condition of the tailing management facilities, as well as for training staff both in the governance bodies and in mining enterprises.

The Agrihood Design: Valuation of Ecosystem Services for NbS Visions in Peri-urban Housing Estate Development, Bangkok, Thailand

Nature-based Solution (NbS) designs increasingly are being implemented to reduce environmental impacts of urban development and enhance community resiliency to disruptions ranging from floods to climate change to Covid-19. But, the question remains, how do we assess the ecosystem service benefits provided by competing NbS designs in order to optimize such benefits? As such, the objective of this study was to develop and trial an assessment approach for the valuation of ecosystem services in a peri-urban area of Bangkok, Thailand. In our evaluations we considered the ecosystem service benefits of: i) water yield; ii) sediment yield; iii) nutrient yield; iv) carbon sequestration; v) urban heat island mitigation; vi) crop production; vii) habitat quality; and viii) aesthetics. Our ecosystem services valuation approach was tested using three case studies in peri-urban Bangkok, Khlong Luang, Pathum Thani: i) an existing new single detached housing development in the area; ii) an area in its currently undeveloped, open and scrub forest state; and iii) the same area as (ii), but theoretically developed using an Agrihood design concept. The valuation approach included a combination of mathematical modeling for the water, sediment, and nutrient yield ecosystem services and an empirical, data-driven approach for urban cooling, carbon sequestering, crop production, habitat quality, and aesthetics. While the existing housing development design was meant to be relatively green and nature-oriented, the Agrihood design outperformed it in every ecosystem service category, including habitat quality and aesthetics. The Agrihood design also had lower sediment and nutrient yields and mean concentrations as compared to current (natural) conditions at the site, which is attributed to the inclusion of constructed wetlands in the design for the main drainage canal. This work represents a good preliminary step in establishing a local scale ecosystem services valuation framework for urban areas in a tropical climate, but additional refinements to the indicator determinations are needed.

Concentration of some heavy metals in main irrigation and drainage canals water of Bakolori irrigation project, Zamfara state, north western Nigeria

Concentration of Some heavy metals in main irrigation and drainage canals water of Bakolori Irrigation Project (BIP) were investigated from March 2019 to February 2020. Four sampling stations were systematically & randomly selected from the two canals respectively. Water samples were collected monthly from the eight sampling stations and taken to the laboratory for analysis of Cadmium (Cd), Chromium (Cr), Copper (Cu), Iron (Fe), Manganese (Mn), Lead (Pb) and Zinc (Zn). The data collected were arranged on the bases of two seasons (dry & wet) and five sub-seasons, namely: Early dry (Oct - Dec); mid dry (Jan & Feb); late dry (March - May); Early rainy (June & July) and flood period (Aug & Sept), and subjected to T test (p

Assessment of a Coastal Aquifer in the Framework of Conjunctive Use of Surface Water and Groundwater—The Case of the River Nestos Western Delta, NE Greece

This paper presents research regarding the assessment of the hydrogeological system of the River Nestos Western Delta, NE Greece, during the period of 2019. The procedure included the collection and analysis of relevant hydrological and hydrogeological data concerning the aquifer system of the study area. Specifically, groundwater level measurements and sampling were carried out in a monitoring well network in the shallow unconfined and the deep confined aquifers of the study area, respectively; and surface water sampling was conducted from the River Nestos at selected locations in each of the main drainage canals, as well as in lagoons of the study area; followed by analysis and processing of the relevant chemical analyses results. Finally, piezometric, hydrochemical maps and diagrams were constructed to augment the evaluation of results and the assessment of the system. The present study contributes to the development and management of water resources in the River Nestos Delta area by providing insight into the hydrodynamic and hydrochemical status of the system based on comprehensive contemporary data that can support and justify the compilation of realistic measurements. The conjunctive management of the surface and groundwater in the study area can improve the quantitative and qualitative characteristics of the water. The water level in piezometric maps varies from −4 m up to 16 m for both time periods (May 2019 and October 2019). Moreover, the maximum values of EC are 2700 μS/cm and 2390 μS/cm for the confined and unconfined aquifer systems, respectively. The maximum values of Cl− concentrations are 573.89 mg/L for the confined aquifer system and 514.73 mg/L for the unconfined aquifer system for both time periods (May 2019 and October 2019).

Microbial marker for seawater intrusion in a coastal Mediterranean shallow Lake, Lake Vrana, Croatia

Climate change-induced rising sea levels and prolonged dry periods impose a global threat to the freshwater scarcity on the coastline: salinization. Lake Vrana is the largest surface freshwater resource in mid-Dalmatia, while the local springs are heavily used in agriculture. The karstified carbonate ridge that separates this shallow lake from the Adriatic Sea enables seawater intrusion if the lakes' precipitation-evaporation balance is disturbed. In this study, the impact of anthropogenic activities and drought exuberated salinization on microbial communities was tracked in Lake Vrana and its inlets, using 16S rRNA gene sequencing. The lack of precipitation and high water temperatures in summer months introduced an imbalance in the water regime of the lake, allowing for seawater intrusion, mainly via the karst conduit Jugovir. The determined microbial community spatial differences in the lake itself and the main drainage canals were driven by salinity, drought, and nutrient loading. Particle-associated and free-living microorganisms both strongly responded to the ecosystem perturbations, and their co-occurrence was driven by the salinization event. Notably, a bloom of halotolerant taxa, predominant the sulfur-oxidizing genus Sulfurovum, emerged with increased salinity and sulfate concentrations, having the potential to be used as an indicator for salinization of shallow coastal lakes. Following summer salinization, lake water column homogenization took from a couple of weeks up to a few months, while the entire system displayed increased salinity despite increased precipitation. This study represents a valuable contribution to understanding the impact of the Freshwater Salinization Syndrome on Mediterranean lakes' microbial communities and the ecosystem resilience.

Occurrence of Eggs Spawned by Cyprinidae Fish Species in Improved Main Drainage Canals and Streams Flowing into Northeast Shores of Lake Biwa

Occurrence of Eggs Spawned by Cyprinidae Fish Species in Improved Main Drainage Canals and Streams Flowing into Northeast Shores of Lake Biwa

Land degradation by erosion occurred after irrigation development in the Harran plain, Southeastern Turkey

A study was made to determine the erosion problem and determine the amount of suspended sediment transport in the drainage channels of the Harran Plain by conducting periodic suspended sediment sampling and discharge measurements in the field between 1997 and 2017. When irrigation in the Harran Plain started in 1990, the production of the agricultural goods quadrupled within a few years. Unfortunately, excessive amounts of irrigation water supplied to irrigate crops also led to the erosion of the soil in the fields by surface runoff. Furthermore, the mixture of clay, silt, and fine sand in the topsoil from certain areas accumulated in the tertiary and secondary drainage systems and reduced the effectiveness of the drainage system. Analysis of the suspended sediment measurements between 1997 and 2017 showed that the yearly averaged sediment transported to Syria by the main drainage canal of the Harran Plain varied between 128 ton.day−1 to 1268 ton.day−1, and the average of the 21-year measurement is about 682 ton.day−1. The logarithmic plot of the suspended sediment rating curve showed that as the discharge of the Cullap Creek increases, the sediment transport rate also increases linearly. It means excess furrow irrigation could cause substantial topsoil loss. Sediment erosion resulting from rainfall events in the Harran Plain is also computed using Revised Universal Soil Loss Equation (RUSLE). The results showed that rainfall erosion from the Harran Plain is 131.5 ton.day−1. A comparison of this value with the 21-year value of average sediment erosion by irrigation shows that approximately 20% of sediment erosion from the Harran Plain was caused by rainfall events, and the remaining 80% was caused by excess irrigation water in the area. A 2D numerical model was constructed with MIKE 21 software applying Van Rijn Method to calculate suspended sediment load due to irrigation, and it allowed to calculate the load with a 6.47% error. Grouping the irrigated and non-irrigated periods and applying independent t test, a statistical approach constituted and resulted in 79.2% of suspended sediment load is caused by irrigation. The numerical model and statistical analysis supported the findings of field data and RUSLE Model results. The study showed that the main reason of the topsoil loss in the Harran Plain is the excess furrow irrigation.

Seasonal levels of pesticide residues in the main and the Blue Nile waters in Sudan

Levels of twenty-two commonly used pesticides were monitored three times a year (autumn, winter, and summer) in 54 water samples collected from six sites representing the main and Blue Nile. These sites were selected to reflect any attributes from main drainage canals from agricultural schemes in Sudan as well as any impact from upstream sources. Collected samples were subject to gas chromatographic analysis equipped with FID/ECD, and results were expressed in ng/l water. Analysis of Blue Nile water indicated the presence of OCs in 45% of the samples, OPs in 11%, pyrethroids in 22%, and none of the tested herbicides. Heptachlor and DDTs were the most prevalent followed by the pyrethroids. Levels detected were not high. Water of the main Nile showed the presence of OCs in 22% of the samples, pyrethroids in 4%, and none of the tested OPs and herbicides. DDT is the most prevalent followed by heptachlor. Total concentration in main Nile is relatively higher than the Blue Nile. Residues of DDD, λ cyhalothrin, deltamethrin, oxyfluorfen, HCH, and endosulfan isomers were not detected in the analyzed samples. Generally levels were least in autumn, followed by summer and winter. Sources of contamination might include some drains from agricultural lands in central Sudan and/or upstream sources. Both recent and old contaminations were indicated.

Experiments on Efficiency Review of New-Type Screens for Waste Treatment in the Drainage Canal

Yoon, J.-S.; Park, J-H.; Cho, Y.K.; Ha, T., and Lee, J.H., 2019. Experiments on efficiency review of new-type screens for waste treatment in the drainage canal. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 266-270. Coconut Creek (Florida), ISSN 0749-0208.Drainage canals installed for irrigation in farms are helplessly exposed to reckless garbages and municipal wastes. In addition, according to “Design Standards for Agricultural Drainage (2012)” of the Korean Ministry of Agriculture, Food and Rural Affairs, drainage canals with inlet flow below 5 m3/sec cannot use dust collectors, causing issues related to treatment of municipal wastes that accumulate in drainages. This study proposed a method of collecting municipal wastes by installing a separate dust collecting canal and screen in drainage canals as an alternative solution to these issues, and their efficiency was analyzed by a hydraulic model test. The hydraulic model test analyzed hydraulic characteristics according to different shapes (screen installation angle, screen blade angle) of screen I in the main drainage canal and the clogging of screen II in the dust collecting canal. The effect of collecting municipal wastes entering into the dust collecting canal was reviewed by applying the LS-PIV (Large Scale Particle Image Velocimetry) technique. Result of the hydraulic model test, highest efficiency was shown when length of screen I became longest with installation angle of 15° and blade angle of 30°. The concerned back-water phenomenon did not occur.

Ecological diversity of sediment rhizobacteria associated with Phragmites australis along a drainage canal in the Yellow River watershed

Spatial distribution on a regional scale of the rhizobacterial communities of Phragmites australis stands was investigated along the Yellow River watershed, China. Samples were collected along a secondary and the main drainage canals. Amplified ribosomal intergenic spacer analysis (ARISA) and pyrosequencing were performed to study the diversity of microbial communities. Bacterial functionality was characterized using a functional inference-based (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States, PICRUSt) approach. Microbial community structure resulted to be primarily driven by phosphorus, nitrogen, mercury, chromium, and nickel. At genus level, taxa related to bioremediation, in particular Thiobacillus and Flavobacterium, and plant growth-promoting bacteria, such as Lysobacter, were found to be stably associated with P. australis. Genera related to fecal contamination such as Faecalibacterium, were recorded in three sampling sites. Rhizobacterial communities showed a significant fraction of taxa related to the xenobiotic metabolism and degradation. Rhizobacterial communities were influenced by the multiple effects of the different environmental parameters. Moreover, the rhizosphere of P. australis can be considered potentially a source of bacterial taxa useful for bioremediation and growth-promoting activities of plants.

Environmental Impact of Anthropogenic Activities on the Surface Water Resource and Evaluated For Drinking and Domestic Uses around the River Nile, Assiut Governorate: Upper Egypt

The main aim of the present study is to study the Impact of Anthropogenic Activities on the Surface Water Resource in Assiut Governorate, and detecting the source and contamination level and evaluating for different purposes. To achieve this goal, collect 30 surface water samples from surface water resources (main irrigation, drainage canals and River Nile) in Assiut Governorate during autumn season 2013. Chemical analysis cared out at Geology Department - Faculty of Science - Minia University and Environmental Affairs Agency. The resulted data revealed that the worst samples are the samples No. 6, 10, 14, 15, 18, 20, 29 and 30 especially simple No. 18. Ni and As showing relatively high values in the most of the surface water samples in study area. Most surface water resources receive large amounts of wastewater, presence of pollution especially organic pollution. Also, it refers to high concentrations of some heavy metals. The source of these pollutants is wastewater from sewage, industrial and agricultures activates. Most surface water samples are unsuitable for human drinking without treatment because it's higher content of trace elements (Fe, Mn, NH4, B, Cd, Ni, and Pb) According to permissible limits for drinking water quality. Only 10% of surface water samples are suitable for laundry purposes (range of moderate hardness) and the rest are hard or very hard. All surface water samples are suitable (Excellent) for livestock and poultry. The recommends of this study are the management of pollution sources, application of Agrochemicals and controlling the seepage of wastewater from rural, protecting the area around the outlet of drinking water treatment plants. Continuous monitoring of water resources using for different purposes.

博斯腾湖农田排水及其污染物空间分布特征分析

博斯腾湖曾经是我国内陆最大的淡水湖泊，也是焉耆盆地、孔雀河沿岸及塔里木河下游的重要水源地。自上世纪五十年代以来，随着工农业的发展，经农田排水进入湖泊的污染物增多，水质开始劣化。农田排水是造成湖水污染最主要的原因。为定量辨析农田排水污染特征的空间分布及其近年来的年际变化，本文首先基于遥感影像，结合实地调查，绘制了26条主要排渠的空间分布图；其次根据2002年6月至2003年5月的农田排水监测数据对农田排水量及各种污染物含量进行估算；最后，选取8条主干渠将其与2007年前人的估算结果进行了对比。研究结果表明：1) 26条排渠的污水排放总量、TN和TP含量分别为4.3亿m3、1287 t和10 t；2) 进入大湖区的17条排渠中，黄水总干排的污水排放量和TP含量最大，分别为1.35亿m3和4.3 t；而TN含量最大的为22团南干排，为296 t；3) 依据26条排渠的水质数据，选取单因子指数法对其污染浓度进行水质评价，并对污染因子的浓度进行排序；4) 选取8条主干渠，其污水量、TN和TP含量之和分别为3.6亿m3、1193 t和9.6 t。2007年与2002年6月至2003年5月相比，其污水总量、TN和TP含量分别占后者的81.4%、46.0%和527.7%。 Bosten Lake was once China’s largest inland freshwater lake. Also, it is the important water source for the Yanqi Basin, the banks of Qongquehe, and the Tarim River. Since the 1950’s, the develop-ment of industry and agriculture has caused not only increased pollution into the lake, but also the water quality has deteriorated. Farmland drainage is the main cause for the water pollution. To quantitatively analyze the farmland drainage pollution, data were gathered for the characteristics of spatial distribution and for the annual changes in recent years. The following items below were used for obtaining these data: First, there is the basis of the remote sensing images and the field survey, where we represent the GIS’s plotting for the 26 main drainage canals. Secondly, by using the monitoring data of the drainage water into the lake during the period of June 2002 to May 2003, we can approximately estimate the increased amounts of wastewater and pollutants. Then lastly, we will use the results of the eight most important canals to be compared with the data for the year 2007. The criteria set above helped produce the following information: 1) The total drainage volume of wastewater, TN, and TP content of 26 main drainage canals was 4.3 × 108 m3, 1287 t and 10 t respectively; 2) For the 17 drainage canals into the Lake, the Yellow Main Dry Line had the largest total drainage volume of wastewater and TP content, 1.35 × 108 m3 and 4.3 t respectively; while the largest TN content was at the 22nd South Dry Line, 296t; 3) The grades of water quality for all of the drainage canals have now been classified and then arranged by the single factor index method and by the concentration of the pollutants; 4) Among all the drainages, we have selected eight most important canals whose total drainage volume of wastewater, TN, and TP content were respectively 3.6 × 108 m3, 1193 t and 9.6 t. Therefore, by comparing the data obtained from the year 2007 with those obtained from the period of June 2002 to May 2003, we have found that the percentage increase of wastewater, TN, and TP content was respectively 81.4%, 46.0% and 527.7%.

Water Quality of Drainage Canals and Assessment of Nutrient Loads Using QUAL2Kw

The water quantity and quality in two of the four main drainage canals located in the plain of Chryssoupolis in Kavala, North Greece, are studied. The area is intensively used for agriculture. Irrigation water is supplied by Nestos River, using a network of irrigation canals. Drainage water and irrigation return flows are collected in the four main drainage canals, which outflow into the Thracian Sea, North Aegean. A monitoring program in the four canals was designed to monitor flow and main constituents of drainage water. Main pollutants included nitrate, phosphorus and suspended solids. Based on the collected data, the trophic state of the canals and its seasonal variation were assessed, and the limiting nutrient was identified. QUAL2Kw was also used to model flow and water quality in two of the four canals. The calibration and verification of QUAL2Kw was undertaken using the collected field data, in an effort to identify the pollution sources and propose future management actions for the improvement of drainage canal water quality. The results showed that QUAL2Kw is a useful tool to simulate water quality in rivers and canals, and to quantify the impacts of non-point source pollution from agricultural areas.

Hydraulic models for the simulation of flow routing in drainage canals

<p>In order to design a network of drainage canals, it is essential to consider the excess water from the agricultural land (overland flow) and to evaluate the characteristics of flow routing, such as the flow depths and discharges in the system of tertiary and main drainage canals of various order. In this paper models based on the Saint-Venant equations are presented, simulating the flow routing in a system of drainage canals. In these models, the lateral inflow towards tertiary drainage canals is the overland flow from adjacent fields. The Saint-Venant equations in their complete form (dynamic model) or in simplified forms, such as the diffusion wave equations (diffusion model) and the kinematic wave equations (kinematic model) are numerically solved by using the MacCormack explicit computational scheme which is a two-step predictor-corrector scheme, conditionally stable and convergent. In modeling flow through the system of drainage canals, emphasis was given to the simulation of flow at the junction points of two or more canals by applying the characteristic equations (negative and positive equations) in addition to the mass and energy conservation principles. Applications of the models for the simulation of flow within the system of drainage canals, subject to lateral inflow owing to overland flow, were also conducted in order to study the effect of various parameters of the drainage canals, on the hydrographs’ formation and also on the accuracy of the diffusion and kinematic equations in predicting flow in a drainage network.</p>

Seasonal changes of fertilizer impacts on agricultural drainage in a salinized area in Adana, Turkey

Seasonal changes in the impacts of fertilizer on the composition of agricultural drainage water were examined by analyzing the 87Sr/ 86Sr isotope ratio and chemical composition of drainage water samples. Samples of drainage water were taken from the main drainage canals of the Lower Seyhan Irrigation Project, at sites designated as D10, D11, and D12. Plots of 87Sr/ 86Sr vs. 1/Sr indicated that the 87Sr/ 86Sr ratio of drainage water was positively related to those of fertilizer and irrigation water. The origins of Sr in two of the end-components were fertilizer and irrigation water. The data from the end-drain in winter suggested that the origin of Sr in the third end-component was fossil seawater. Analysis of a mixing model incorporating these three end-components showed that the origins of Sr in drainage differed markedly between summer and winter. Fertilizer made the greatest contribution to Sr in drainage water both in summer and winter, contributing 38–72% of total Sr in summer and 64–87% of total Sr in winter. In summer, fertilizer contributed 72% of total Sr in drainage water in D12, 44% in D10, and 38% in D11. This result implies that fertilizer was applied excessively at the D12 site. In winter, seawater accounted for 10% of Sr in drainage water in D12, whereas it accounted for 19–27% of Sr in drainage water in D10 and D11. Therefore, at least 70% of the salt in drainage water originates from fertilizer and irrigation water. At this study site, the salt originating from seawater is replaced by that from fertilizer and irrigation water, due to intensive agricultural management. The study site is a delta that lay on the ocean subsurface at least 3000 years ago, and therefore, was originally a primary salinization area. This result suggests that anthropogenic secondary salinization progressed over time via fertilizer and irrigation applications.

Estimation of water levels in a main drainage canal in a flat low-lying agricultural area using artificial neural network models

The Chiyoda basin is located in the Saga Prefecture of the Kyushu Island, Japan, and lies next to the tidal compartment of the Chikugo River, into which excess water in the basin is drained away. This basin has a total area of approximately 1100 ha and is a typical flat and low-lying agricultural area. The estimation of the water levels at the gates and along the main drainage canal is a crucial issue that has recently been the subject of much research. At these locations farmers and managers need to control the operation of the irrigation and drainage systems during periods of cultivation. An attempt has been made to apply a feed-forward artificial neural network (FFANN) to model and estimate the water levels in the main drainage canal. The study indicated that the artificial neural network (ANN) could successfully model the complex relationship between rainfall and water levels in this flat and low-lying agricultural area. Input variables and the model structure were selected and optimized by trial and error, and the accuracy of the model was then evaluated by comparing the simulated water levels with the observed ones during an irrigation period in July 2007. The water levels at two locations, located upstream and downstream of a main drainage canal, were investigated by using a time series at intervals of 20, 30, and 60 min. At these intervals, rainfall and tide water levels in the Chikugo River were measured, and the backward time-step numbers of the input variables of rainfall and tide water level were searched. For the upstream location, the optimal combination yielding good agreement between the observed and estimated water levels was obtained when the interval of the time series was 60 min. The number of backward time-steps of the input variables of rainfall and tide water level were 5 and 4, respectively. In contrast to the downstream location, the optimal combination was obtained for the interval time series of 20 min with 4 backward time-steps for both the input variables of rainfall and tide water level. The present study could provide farmers and managers with a useful tool for controlling water distribution in the drainage basin, and reduce the cost of installing water level observation points at many locations in the main drainage canal.

Optimal gate operation of a main drainage canal in a flat, low-lying, agricultural area using a tank model

Chiyoda basin is located in Saga Prefecture in Kyushu Island, Japan, and lies next to the tidal compartment of the Chikugo River to which the excess water in the basin is drained away. Chiyoda basin has a total area of about 1,100 ha and is a typical flat and low-lying paddy-cultivated area. The main problem in this basin is the appropriate operation of drainage structures during and after flood events in order to minimize the inundation damages for crop yield and to fulfill the irrigation requirement in the irrigation period. This paper presents a mathematical model of a drainage system in Chiyoda basin for calculating the flood inundation and optimizing the operation of gates in a main drainage canal. First, the algorithm of gate operation was simulated and the drainage model was then evaluated by comparing the simulated water levels with those observed during an actual rainfall event. The results show that the observed and simulated water levels are in good agreement, indicating that the proposed model is applicable for drainage and inundation analyses in flat, low-lying paddy-cultivated areas. Second, the optimization of gate operation was investigated by trial and error method using a stochastic rainfall time series with a return period of 30 years and the tidal conditions of spring and neap tides in the Chikugo River. Comparing a total inundation time, a total inundation area and maximum inundation depth in the paddy tanks at the upstream and the downstream ends, it was concluded that the present operation based on the gate operators’ experience was almost the optimal one, and the sooner start of opening operation and the later start of closing operation within the operationality of check gates were recommended to minimize the inundation damage. The present operation could be able to minimize the total inundation time, the total inundation area and the maximum inundation depths in paddy tanks and to meet fully both the drainage and the irrigation requirements.

幹線排水路における魚類の出現パターンに影響する要因―岩手県胆沢町の「原川排水路」土水路区間を事例として―

This study clarified the relationships between appearance patterns of fishes and environmental factors in the main drainage canal in Isawa Town, Iwate Prefecture. Appearance patterns of fishes were most diverse in the environments with high openwork gravel rate and deeper water. It was because of an indispensable condition for fishes of which habitat in the space between gravel and fishes of which habitat was deeper water like pool. We discussed it was important to maintain the environmental factors such as the openwork gravel and pools to secure fish diversity.

Landscape-Scale Simulation of Pesticide Behavior in River Basin due to Runoff from Paddy Fields Using Pesticide Paddy Field Model (PADDY)

A landscape-scale simulation model (PADDY-Large) based on PADDY was developed for predicting pesticide concentrations in drainage canals and rivers due to runoff from paddy fields. Based on the irrigation systems used in agrohydrology, a rice-producing area was classified into a “field plot”, “farm block”, “district”, and “river basin” and pesticide behavior was estimated focusing on the main drainage canals in the “district” area. To validate the model, a surveillance of pesticide residues was carried out in a rice-producing area. Herbicide concentrations in a main drainage canal in the area increased in early May, reached a maximum in mid May, and declined to below detection limits by early July. The correlation between simulated and observed concentrations of a herbicide mefenacet in the main canal were obtained by considering actual pesticide use and environmental conditions in the rice-producing area.

Hydraulic Analysis of a Self-Cleaning Drainage Outlet at the Hellenistic City of Priene

At the distal western end of a main drainage canal running along West Gate Street in the Hellenistic city of Priene, an unusual masonry outlet structure has been found. The housed structure contains a doubly curvilinear, contracting rectangular cross-section flow passageway that allows drainage water flow through the city perimeter wall. A computer model of the complexly-shaped drainage structure has been hydraulically analysed in order to determine the function of the curvilinear passageway. Results indicate that the internal shaping of the structure hydraulically conditions the flow to create multiple circulatory mixing flows that agitate and entrain debris in the outflow stream sufficient to “self-clean” the outlet, thus preventing clogging. Further calculations of flow free surface shapes at different flow rates indicate the maximum flow capacity that can be processed by the drainage system without overspillage to provide a lower-bound estimate of the steady-state water supply to the city. The design of a self-cleaning, continuous flow urban wastewater system implies that Greek city planners maintained a high level of awareness about the hygienic conditions needed to maintain the health of the populace. The Greek attitude toward technical refinements necessary to improve the quality of urban life could therefore not be better represented than in attention to detail related to water supply and waste water drainage systems as a key to improved life standards.