Increasing areas of aquaculture ponds and reservoirs reshape runoff coefficients: evidence from a subtropical catchment, China.

Detention pond is a key storm water management measure employed both to attenuate surface runoff and to regulate depression storage, yet the effects of aquaculture ponds and reservoirs on runoff coefficient are not well quantified in a subtropical humid monsoon climate zone, China. Here, a set of six subcatchments ranging in size from 0.7 hm2 to 10,000 hm2 were evaluated over the 2011-2015 period. (i) The annual average runoff coefficient differed with different subcatchments due to the spatial heterogeneity of landscape patterns, while the event-based runoff coefficient under the same catchment showed a decreasing trend with increasing rainfall intensity. (ii) The annual average and event-based runoff coefficients initially increased and then decreased with an increase in the area ratio of aquaculture ponds and reservoirs. The critical area ratio of aquaculture ponds and reservoirs for the maximum runoff coefficient in annual, light, and moderate rainfall intensity was about 4%; but this value would be transferred forward to the position of < 4% under the intensity of heavy rain, rainstorms, and heavy rainstorms. (iii) All runoff coefficients decreased with increasing forestland but increased with increasing paddy fields, and the decreasing rate was greater than the increasing rate. The trends of runoff coefficient for the annual and event-based rainfall are opposite between river development coefficient and watershed shape coefficient. The results provide underlying insights for decision-makers in aquaculture land-use planning and the sustainable utilization of water resources in the upstream and downstream systems of a catchment.

Identification of suitable zones and sites for rainwater harvesting using GIS and multicriteria decision analysis.

Identifying suitable zones for surface water storage and groundwater recharge is needed to enhance irrigation water availability. This study was undertaken to map rainwater harvesting (RWH) potential zones using geospatial tools and analytic hierarchy process (AHP). The suitable locations for RWH were also mapped using the Boolean logic concept. The surface runoff is a vital factor to demarcate the appropriate zones for RWH. The curve number approach was used to estimate the surface runoff potential. The runoff coefficient (RC) map was generated based on rainfall and surface runoff depth. Weights have been allocated to selected themes of RC, drainage density, and slope. The themes were integrated using geographic information system (GIS) and AHP to demarcate the suitable zones for RWH. The derived RWH potential map was categorized into zones like "very good," "good," "moderate," "poor," and "very poor" with an aerial extent of 14.3%, 24.7%, 28.3%, 20.2%, and 12.6%, respectively. The area suitable for farm ponds was found to be about 9% (408 km2), 13% (329 km2), and 4% (244 km2) in Mirzapur, Chandauli, and Sonbhadra districts, respectively. Furthermore, 22, 15, and 21 locations were found suitable for check dams in Mirzapur, Chandauli, and Sonbhadra districts, respectively. At a large scale, effective planning of water management strategies based on multicriteria decision analysis and GIS offers increased availability of surface and groundwater resources and may help for enhancing the agricultural land use options. The higher resolution maps may be further utilized to plan RWH strategies at village level.

Mathematical model for the duration of runoff formation determined from the road surface.

INTRODUCTION: Many scientists were engaged in the problems of studying the runoff formation conditions from the water-intake basins area and studying the operation of rainwater drainage systems and its calculations. Among them: Alekseev M. I., Belov М. М., Dykarevskyi V. S., Kurganov А. М., Zhuk V. M., Tkachuk S. G., Salchuk V. L., Tkatchuk O. A., Shevchuk O. V., Dziopak J., James W., Horton R., Huber W., Mays L. W., Rossman L. A., Weitman D. [1-9] and others. The drainage systems calculation is implemented based on empirical or semi-empirical studies for pipes or open water bodies. Unlike the generally accepted conditions for the urban city areas drainage elements calculation, highways have the features of runoff and the formation of maximum runoff. Artificial surfaces of surface runoff are characterized by low water absorption, significant longitudinal and transverse slopes. According to State Building Norms DBN V.2.3-4:2015 «Highways. Part I. Design. Part II. Construction¼, the largest longitudinal slope for a category I road is 40 %, the carriageway transverse slope on straight sections is 25 %. In the world of engineering practice there is no single generally accepted approach to the construction of hydrographs of rainwater inflow to surface drainage structures. Therefore, the question remains open in terms of establishing the estimated rain duration and the surface runoff volume from the roads surface in particular. GOAL AND PROBLEM: To explore and establish the main factors and their parameters for the surface runoff formation from road surfaces. RESEARCH METHODS: In engineering practice, forecasting the estimated rain duration is defined as the time from its beginning to the time of collection by the drainage system. This research is based on the prediction method and analysis of the factors, which influence the effluents movement on the coating surface of the linear in the plan water-intake basins. Conducting research with the forecasted natural meteorological phenomenon and at the minimum estimated rain intensity values according to climatic conditions of Ukraine. RESULTS: The analysis of known methods for duration of surface runoff formation determining performed. For its determination, it is suggested to take into account the surface wetting duration and the influence of the viscous component of the friction force between the runoff layers. An analytical dependence for the surface runoff formation duration determining for highways with asphalt concrete pavement and variable longitudinal slope in the range from 0‰ to 30‰ is obtained. The influence of wastewater viscoelastic properties is determined. The influence of the calculated precipitation intensity on the surface runoff formation duration for linear water-intake basins is determined. CONCLUSIONS: A mathematical model for determining the surface runoff formation duration for linear water-intake basin, namely highways, taking into account the estimated highway slope, the width of the carriageway, the estimated rainfall. A comparative analysis with existing methods is performed.

Simulating the change of precipitation-runoff relationship during drought years in the eastern monsoon region of China.

Most hydrological simulation and prediction methods assume that the precipitation-runoff relationship was stationary. However, this assumption was found to be questionable during drought years: the annual runoff coefficients (the ratio of annual runoff to annual precipitation) during drought years tend to be smaller than those during non-drought years. However, little is known about the spatial distribution of the magnitude of runoff coefficient change (RCchange) during drought years, and which factors dominate the spatial pattern of RCchange over a large spatial scale. To answer these questions, this study investigated the RCchange in 265 catchments in China that cover a broad range of climate and landscape conditions. We identified the significant factors affecting RCchange from ten catchment characteristics and developed a multivariate generalized additive model to simulate the spatial pattern of RCchange across the eastern monsoon region of China. Results indicated that the RCchange showed an increasing trend from north to south of China, with values ranging from -67.1% to -0.3%, with the average being -26.4%. The lower RCchange (corresponding to more significant runoff reduction) in drought years was more likely to occur in catchments with dryer climate and lower elevation. The simulated RCchange by the multivariate generalized additive model demonstrated a good agreement with observed RCchange, and the values of Nash-Sutcliffe efficiency between observed and simulated RCchange were 0.77 for training catchments and 0.72 for testing catchments. Finally, we applied the model to extrapolate RCchange to the entire eastern monsoon region of China. The result would benefit water resources management during drought years.

Effects of rainfall and terracing-vegetation combinations on water erosion in a loess hilly area, China.

Terracing and vegetation restoration are the basic measures to protect soil from water erosion and to combat land degradation. However, long-term quantitative evaluation on the erosion control benefits of different terracing techniques and vegetation types are still insufficient, particularly under variable rainfall. The aim of this article, therefore, is to evaluate the coupling effects of different terracing-vegetation combinations and rainfall types (RTs) on runoff retention and erosion reduction in a loess hilly catchment of China. Six types of terracing-vegetation combinations, including leveled benches-C. microphylla (LM), fish-scale pits-P. orientalis (FO), leveled ditches-P. armeniaca (LA), zig terraces-P. orientalis (ZO), fish-scale pits-P. tabulaeformis (FT), zig terraces-P. tabulaeformis (ZT) and the corresponding plots with same vegetation cover and non-terracing measures were designed and monitored. Based on five consecutive years of monitoring data, 69 rainfall events causing runoff and erosion were observed. Rainfall eigenvalues, including rainfall amount (RA), maximum 10-min intensity (I10), maximum 30-min intensity (I30) and rainfall duration (RD) dominated water erosion processes. Surface runoff and sediment reduction benefits differed with different terracing techniques. Mean runoff coefficients (Rc) among all kinds of terracing-vegetation combinations were FT > LM > FO > LA > ZO > ZT, while mean soil loss rates (Em) among all kinds of combinations were FT > FO > LM > LA > ZT > ZO. ZT showed the highest mean runoff reduction (44.03%), while ZO generated the highest sediment reduction (39.08%). The worst performance was observed in FT. With regards to the results, it is necessary to select the optimal terracing-vegetation measures for erosion control based on the dominant rainfall eigenvalues in different areas. Overall, ZT, ZO and LA combinations are recommended, while uncertainty was detected in combinations with fish-scale pits. Suitable terracing-vegetation measures should be selected after considering the micro-relief construction, the optimization of plant disposition and the efficiency of water erosion reduction. Management should focus on the construction standards, the threshold of resisting erosion for each terracing measure, and timely maintenance of the terraces.

Spatial and temporal variability of event runoff characteristics in a small agricultural catchment.

The objective of this study is to investigate the factors that control event runoff characteristics at the small catchment scale. The study area is the Hydrological Open Air Laboratory, Lower Austria. Event runoff coefficient (Rc), recession time constant (Tc) and peak discharge (Qp) are estimated from hourly discharge and precipitation data for 298 events in the period 2013-2015. The results show that the Rc and their variability tend to be largest for the tile drainages (mean Rc = 0.09) and the main outlet (mean Rc = 0.08) showing larger Rc in January/February and smaller Rc in July/August. Tc does not vary much between the systems and tends to be largest at the main outlet (mean Tc = 6.5 h) and smallest for the tile drainages (mean Tc = 4.5 h). Groundwater levels explain the temporal variability of Rc and Tc more than soil moisture or precipitation, suggesting a role of shallow flow paths.

Avaliação do escoamento superficial de águas pluviais em pavimento de blocos de solo-cimento / Assessment of stormwater runoff in pavement of soil-cement blocks

RESUMO Avaliou-se o coeficiente de escoamento (volume escoado/volume precipitado), que define a capacidade de redução do escoamento superficial de um pavimento com blocos de solo-cimento intertravados (20,7 m de comprimento e 3 m de largura) dentro de uma estrutura de vigas de concreto transversais implantada em uma área de declividade de 6% e solo de baixa permeabilidade, e condições similares em áreas de ocupação de populações de baixa renda. Cento e oitenta e quatro eventos (precipitações) foram registrados, mas somente foram considerados eventos com volume precipitado maior que a capacidade máxima de armazenamento do pavimento (≈ 1.500 L) e temperatura menor a 23ºC para manter a precisão do sensor de medição. Os valores experimentais do coeficiente C oscilaram na faixa de 0,47 a 0,79, que confirmam que o pavimento de bloco de solo-cimento é semipermeável.

ABSTRACT In this article, the authors assessed the runoff coefficient C (drained volume/volume precipitate), which defines the capacity reduction of runoff, of a pavement with soil-cement interlocking blocks (20.7 m long and 3 m wide) within a structure of transverse concrete beams deployed in an area with slope of 6% and low permeability soil, and similar conditions in areas occupied by poor populations. One hundred and eighty-four events (rainfall) were recorded, but only events with a precipitate volume greater than the maximum capacity storage of pavement (≈ 1,500 liters) and a temperature less than 23ºC, to maintain the accuracy of the measurement sensor, were considered. The experimental values of the coefficient C varied in the range of 0.47 to 0.79, confirming that the soil-cement block pavement is semi permeable.

Water planning in a mixed land use Mediterranean area: point-source abstraction and pollution scenarios by a numerical model of varying stream-aquifer regime.

Integrated hydrodynamic modelling is an efficient approach for making semi-quantitative scenarios reliable enough for groundwater management, provided that the numerical simulations are from a validated model. The model set-up, however, involves many inputs due to the complexity of both the hydrological system and the land use. The case study of a Mediterranean alluvial unconfined aquifer in the lower Var valley (Southern France) is useful to test a method to estimate lacking data on water abstraction by small farms in urban context. With this estimation of the undocumented pumping volumes, and after calibration of the exchange parameters of the stream-aquifer system with the help of a river model, the groundwater flow model shows a high goodness of fit with the measured potentiometric levels. The consistency between simulated results and real behaviour of the system, with regard to the observed effects of lowering weirs and previously published hydrochemistry data, confirms reliability of the groundwater flow model. On the other hand, accuracy of the transport model output may be influenced by many parameters, many of which are not derived from field measurements. In this case study, for which river-aquifer feeding is the main control, the partition coefficient between direct recharge and runoff does not show a significant effect on the transport model output, and therefore, uncertainty of the hydrological terms such as evapotranspiration and runoff is not a first-rank issue to the pollution propagation. The simulation of pollution scenarios with the model returns expected pessimistic outputs, with regard to hazard management. The model is now ready to be used in a decision support system by the local water supply managers.

Remote Sensing Assessment of Safety Risk of Iron Tailings Pond Based on Runoff Coefficient.

Iron tailings ponds are engineered dam and dyke systems used to capture iron tailings. They are high-risk hazards with high potential energy. If the tailings dam broke, it would pose a serious threat to the surrounding ecological environment, residents' lives, and property. Rainfall is one of the most important influencing factors causing the tailings dam break. This paper took Chengde Area, a typical iron-producing area, as the study area, and proposed a remote sensing method to evaluate the safety risk of tailings ponds under rainfall condition by using runoff coefficient and catchment area. Firstly, the vegetation coverage in the study area was estimated using the pixel dichotomy model, and the vegetation type was classified by the support vector machine (SVM) method from Landsat 8 OLI image. Based on DEM, the slope of the study area was extracted, and the catchment area of the tailings pond was plotted. Then, taking slope, vegetation coverage, and vegetation type as three influencing factors, the runoff coefficient was constructed by weight assignment of each factor using analytic hierarchy process (AHP) model in both quantitative and qualitative way. Finally, the safety risk of tailings ponds was assessed according to average runoff coefficient and catchment area in the study area. The results showed that there were 124 low-risk tailings ponds, 16 moderate-risk tailings ponds, and 4 high-risk tailings ponds in the study area. This method could be useful for selecting targeted tailings ponds for focused safety monitoring. Necessary monitoring measurements should be carried out for the high-risk and moderate-risk tailings ponds in rainy season.

Urban rainwater runoff quantity and quality - A potential endogenous resource in cities?

Rainwater harvesting might help to achieve self-sufficiency, but it must comply with health standards. We studied the runoff quantity and quality harvested from seven urban surfaces in a university campus in Barcelona according to their use (pedestrian or motorized mobility) and materials (concrete, asphalt and slabs). An experimental rainwater harvesting system was used to collect the runoff resulting from a set of rainfall events. We estimated the runoff coefficient and initial abstraction of each surface and analyzed the physicochemical and microbiological properties, and hydrocarbon and metal content of the samples. Rainfall intensity, surface material and state of conservation were essential parameters. Because of low rainfall intensity and surface degradation, the runoff coefficient was variable, with a minimum of 0.41. Concrete had the best quality, whereas weathering and particulate matter deposition led to worse quality in asphalt areas. Physicochemical runoff quality was outstanding when compared to superficial and underground water. Microorganisms were identified in the samples (>1 CFU/100 mL) and treatment is required to meet human consumption standards. Motorized traffic mostly affects the presence of metals such as zinc (31.7 µg/L). In the future, sustainable mobility patterns might result in improved rainwater quality standards.

Determining the hydrological responses to climate variability and land use/cover change in the Loess Plateau with the Budyko framework.

Understanding and quantifying the impacts of land use/cover change and climate variability on hydrological responses are important to the design of water resources and land use management strategies for adaptation to climate change, especially in water-limited areas. The elasticity method was used to detect the responses of streamflow and runoff coefficient to various driving factors in 15 main catchments of the Loess Plateau, China between 1961 and 2009. The elasticity of streamflow (Q) and runoff coefficient (Rc) to precipitation (P), potential evapotranspiration (E0), and catchment characteristics (represented by the parameter m in Fu's equation) were derived based on the Budyko hypothesis. There were two critical values of m=2 and E0/P=1 for the elasticity of Q and Rc. The hydrological responses were mainly affected by catchment characteristics in water-limited regions (E0/P>1), and in humid areas (E0/P<1), climate conditions played a more important role for cases of m>2 whereas catchment characteristics had a greater impact for cases of m<2. The annual Q and Rc in 14 of the 15 catchments significantly decreased with average reduction of 0.87mmyr(-1) and 0.18%yr(-1), respectively. The mean elasticities of Q to P, E0 and m were 2.66, -1.66 and -3.17, respectively. The contributions of land use/cover change and P reduction to decreased Q were 64.75% and 41.55%, respectively, while those to decreased Rc were 75.68% and 32.06%, respectively. In contrast, the decreased E0 resulted in 6.30% and 7.73% increase of Q and Rc, respectively. The contribution of land use/cover changes was significantly and positively correlated with the increase in the percentage of the soil and water conservation measures area (p<0.05). The Rc significantly and linearly decreased with the vegetation coverage (p<0.01). Moreover, the Rc linearly decreased with the percentage of measures area in all catchments (eight of them were statistically significant with p<0.05).

Transport of three veterinary antimicrobials from feedlot pens via simulated rainfall runoff.

Veterinary antimicrobials are introduced to wider environments by manure application to agricultural fields or through leaching or runoff from manure storage areas (feedlots, stockpiles, windrows, lagoons). Detected in manure, manure-treated soils, and surface and ground water near intensive cattle feeding operations, there is a concern that environmental contamination by these chemicals may promote the development of antimicrobial resistance in bacteria. Surface runoff and leaching appear to be major transport pathways by which veterinary antimicrobials eventually contaminate surface and ground water, respectively. A study was conducted to investigate the transport of three veterinary antimicrobials (chlortetracycline, sulfamethazine, tylosin), commonly used in beef cattle production, in simulated rainfall runoff from feedlot pens. Mean concentrations of veterinary antimicrobials were 1.4 to 3.5 times higher in surface material from bedding vs. non-bedding pen areas. Runoff rates and volumetric runoff coefficients were similar across all treatments but both were significantly higher from non-bedding (0.53Lmin(-1); 0.27) than bedding areas (0.40Lmin(-1); 0.19). In keeping with concentrations in pen surface material, mean concentrations of veterinary antimicrobials were 1.4 to 2.5 times higher in runoff generated from bedding vs. non-bedding pen areas. Water solubility and sorption coefficient of antimicrobials played a role in their transport in runoff. Estimated amounts of chlortetracycline, sulfamethazine, and tylosin that could potentially be transported to the feedlot catch basin during a one in 100-year precipitation event were 1.3 to 3.6ghead(-1), 1.9ghead(-1), and 0.2ghead(-1), respectively. This study demonstrates the magnitude of veterinary antimicrobial transport in feedlot pen runoff and supports the necessity of catch basins for runoff containment within feedlots.

Filling analysis of artificial lateral canals after main canal obturation through three different endodontic sealers

Introduction and Objective: This study aimed to evaluate, in vitro, the filling ability of lateral canals after main canal obturation through three different endodontic sealers. Material and methods: Thirty single-rooted pre-molars were used and, six lateral canals were constructed on proximal surfaces and arranged in pairs at 3, 5 and 7 mm from the apex. After chemo-mechanical preparation, with size #40 memory instrument, the teeth were randomly assigned to three experimental groups, according to the root canal sealer applied: Endofill® (group A), Sealer 26® (group B) and MTA Fillapex® (group C). In all groups, we used active lateral condensation technique with gutta-percha associated with sealer. After obturation, the teeth were radiographed at buccolingual direction and the images were digitized. The analysis of endodontic sealer plug near the lateral canals was performed by calculating the area through Image Tool® software. Results and Conclusion: The data were subjected to parametric (Anova), and nonparametric (Kruskal-Wallis) tests, with significance level of 5%. There was no difference among the tested sealers for filling the lateral canals. Concerning to the positions of lateral canals, no differences were also found among sealer types, except at 7 mm from the apex, where MTA Fillapex® showed a significantly greater filling than Sealer 26®.

Estimativa de área impermeabilizada diretamente conectada e sua utilização como coeficiente de escoamento superficial / Estimate of directly connected impervious areas and its use as runoff coefficient

Neste estudo realizou-se a caracterização do uso e ocupação do solo na cidade de Ribeirão Preto (SP), além da análise detalhada da impermeabilização urbana e conectividade hidráulica dos lotes. Também foi avaliado o coeficiente de escoamento superficial (C) para seis sub-bacias, utilizando-se três métodos com diferentes níveis de precisão. Utilizando-se o Método Racional com os valores estimados de C, calcularam-se os picos de vazão para as sub-bacias. Identificou-se que a impermeabilização cresce com a redução da área do lote. As estimativas de C resultam em diferenças importantes em seus valores, refletindo na previsão da vazão. A utilização de tabelas com C detalhado e no seu limite superior se aproxima dos valores estimados por C AIDC. Recomenda-se estimar C AIDC a partir da área do lote ou pesquisa de campo.

This paper presents a study of characterization of land occupation and its use in the city of Ribeirão Preto (São Paulo), as well as a detailed analysis of the urban imperviousness and hydraulic connectivity of the plots. The runoff coefficient (C) for siz sub-basins was evaluated on the basis of three different definitions. The peaks of outflow for the sub-basins were calculated using the Rational Method with the estimated values of C. It was identified that the imperviousness increases as the area of the plot decreases. The estimative of the C show important differences in its values, influencing the outflow. The use of tables with detailed and maximal C values beyond its superior limitation is equivalent to the values estimated with C DCIA. It is recommended that the C DCIA relative to the area be estimated based on the plot or field researches.