Poor Drainage Conditions Research Articles

1D-2D MODELING OF URBAN FLOODS AND RISK MAP GENERATION FOR THE PART OF HYDERABAD CITY

Abstract. Space for water is now becoming guiding principle of urban planning because urban flooding is the major problem facing by most of the cities in India. Urban development in developing countries like India usually occurs with high population concentrating in small areas, with poor drainage conditions. People occupy floodplain areas in low flood years and when larger flood occurs it causes high damage. The origin for urban floods is floodplains encroachment and unplanned drainage systems. Complexities in the urban environment and drainage infrastructure have an inherent influence on surface runoff. This runoff generates urban flooding which poses challenges to modeling urban flood hazard and risk. As like in river flooding satellite images are not available for unban flooding scenario. So better modelling provides minimizing loss of life and property. The present study focuses on recognizing the highly effected areas which are liable to flooding when extreme rainfall occurs for part of Hyderabad city (Zone XIII). The entire Hyderabad city is divided into 16 zones and each zone having details of existing drain network. A coupled 1D-2D flood modelling approach is used to identify flood prone areas and develop flood inundation and flood risk maps. 1D model for pilot area is developed using storm water management model (SWMM) and coupled with 2D PCSWMM. A web based GIS platform INPPINS is used to geo reference the existing network details and exported to 1D SWMM model. The model is simulated for extreme flood event occurred in past. The simulation run results identifies overflowing drainage nodes and flood inundation maps and risk maps prepared. The flood risk maps identify the low lying areas which need immediate attention in case of emergency. The overflowing nodes suggest the need of improvement of drainage in the area to safely dispose of the storm water and minimize the flooding.

Numerical Study of Standing Wave-Induced Seabed Residual Response with the Non-homogeneous Soil Property

ABSTRACT Sui, T.; Zhang, C.; Zheng, J.; Guo, Y., and Xie, M., 2018. Numerical study of standing wave-induced residual response with the non-homogenous soil property. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 921–925. Coconut Creek (Florida), ISSN 0749-0208. Coastal seabed soil is usually non-homogeneous vertically. Seabed instability may take place under dynamic wave loading which may lead to the marine landslides. Most of the existing models have been limited to the soil oscillatory mechanism for a sandy seabed with relatively large permeability, which neglects the residual mechanism in a silt seabed with poor drainage condition. In this study, based on the Fully-dynamic (FD) seabed model, the numerical invesitgation for standing wave induced non-homogeneous seabed residual response is proposed. The present model is validated based on the flume tests in...

Geomorphological control on podzolisation – An example from a tropical barrier island

We investigated how the geomorphology of coastal barrier islands impacts soil hydrology and drainage at the landscape scale. Ilha Comprida is a Holocene barrier island with a 2.5 km-long cliff that is perpendicular to the coastal shore which provides an ideal condition to study the relation between age, relief, hydrology, and podzol morphology. Five geomorphic units were identified that differed in surface morphology and alignment of ridges and swales. Optical stimulated luminescence (OSL) dating showed that these geomorphic units had growth phases that decreased in age from west to east (Units I-V, from 5250 ± 820 to 325 ± 31 years ago, respectively). The geomorphic units were studied in two parallel 3 km transects on the southern part of the island. Along transect A-B, about 1 km from the southern shore, deep augerings were used to study sedimentary sequence and soil development, while on transect C-D on the southern shore, the continuous cliff exposure allowed more detailed morphological investigation. On all geomorphic units excluding the youngest, podzolisation has been the main soil-forming process. Groundwater level was monitored monthly for two years in 14 deep wells along transect A-B. Groundwater level during the formation of the B horizon was ascertained by determination of Fe. Podzol morphology (color of B horizon and its boundary with the E horizon) generally showed correlation to groundwater levels for both transects, except for the podzols in southwestern part of the island (Unit II). The podzols of Unit II showed an extremely thick (3 m) Bhm horizon devoid of Fe, indicating that they were formed under poor drainage conditions. However, soil morphology (undulating EB horizon boundary) and measured groundwater levels (below the B horizons) demonstrated that drainage has been improved. The extremely thick B horizon (3 m) in those podzols, which was formed in approximately 3000 years, and its genesis is explained by concentrated lateral flow of DOM-loaded groundwater due to the converging ridge alignments found in these units, in combination with a gradual uplift of the southwestern part of the island.

Flexible pavement damage during spring thaw: A field study using the falling weight deflectometer

Spring thaw creates critical performance conditions for pavement networks. The increase of water content in the pavement environment is significant during spring thaw. Combined with poor drainage conditions, material condition variations are triggering factors that accentuate the effect of heavy vehicle loading on pavement response and damage. Two experimental pavement sections were monitored in 2014 and 2015 for temperature and deflections. The section with the lowest structural capacity was found to be more sensitive to thaw weakening. Fatigue damage calculated for this section was found to be 31% higher than the section with the highest structural capacity. Moreover, it was shown that a load reduction in the range of 20% can decrease the total yearly damage by about 7 to 10% for the considered test sections. In general, fatigue damage was found to increase from spring onset to the warmest conditions of the yearly cycle, in July.

DIRECT SHEAR PROPERTIES OF LIGHTLY CEMENTED SOIL - POLYSTYRENE BACKFILL MATERIAL

Geocomposite materials consisting of lightly cemented mixtures of expanded polystyrene beads (EPS) and backfill soils are commonly used as fillers and for the construction of light weight embankments. The constant normal stress (CNS) and constant volume (CV) direct shear parameters as well as the relationship between gradation properties of four residual granular backfill soils and direct shear parameters of lightly cemented mixture of EPS and backfill soils was evaluated. The maximum density and optimum moisture content of the backfill materials ranged from 1850 kg/m3 to 1730 kg/m3 and 9% to 13%, respectively. The addition of 1.5% of EPS per mass of dry soil resulted in maximum density and optimum moisture content of the blended specimens of backfills soils and EPS that varied from 1303 kg/m3 to 1368 kg/m3 and 7% to 9%. For the range of normal stress used, the CNS friction angles of the four light weight composites were greater than the CV friction angles due to changes in initial normal stress and pore water pressure. Results from series of CNS tests show that both the vertical strain induced by consolidation normal stress and the shear induced vertical displacement for consolidation normal stress of 200 kPa and 400 kPa were significantly greater than the magnitudes induced by normal stress of 50 kPa and 100 kPa, due to reduction in bond strength during consolidation. The relationship between friction coefficients of the composites derived from CNS and CV test data and the uniformity coefficient of the backfill soils was non linear and dependent on the ratio of the sand to the gravel fractions. A practical implication of the two mode of tests is that for a composite material to mobilized the same magnitude of CNS friction angle under constant volume condition, a change in soil particle constitution is required. Both CNS and CV shear parameters should be considered in the design of retaining wall and embankments exposed to poor drainage conditions.

Identification of burden hotspots and risk factors for cholera in India: An observational study.

BackgroundEven though cholera has existed for centuries and many parts of the country have sporadic, endemic and epidemic cholera, it is still an under-recognized health problem in India. A Cholera Expert Group in the country was established to gather evidence and to prepare a road map for control of cholera in India. This paper identifies cholera burden hotspots and factors associated with an increased risk of the disease.Methodology/Principle findingsWe acquired district level data on cholera case reports of 2010–2015 from the Integrated Disease Surveillance Program. Socioeconomic characteristics and coverage of water and sanitation was obtained from the 2011 census. Spatial analysis was performed to identify cholera hotspots, and a zero-inflated Poisson regression was employed to identify the factors associated with cholera and predicted case count in the district. 27,615 cholera cases were reported during the 6-year period. Twenty-four of 36 states of India reported cholera during these years, and 13 states were classified as endemic. Of 641 districts, 78 districts in 15 states were identified as “hotspots” based on the reported cases. On the other hand, 111 districts in nine states were identified as “hotspots” from model-based predicted number of cases. The risk for cholera in a district was negatively associated with the coverage of literate persons, households using treated water source and owning mobile telephone, and positively associated with the coverage of poor sanitation and drainage conditions and urbanization level in the district.Conclusions/SignificanceThe study reaffirms that cholera continues to occur throughout a large part of India and identifies the burden hotspots and risk factors. Policymakers may use the findings of the article to develop a roadmap for prevention and control of cholera in India.

Concentrations of trace elements and iron in the Arctic soils of Belyi Island (the Kara Sea, Russia): patterns of variation across landscapes.

The concentrations of several trace elements and iron were determined in 26 soil samples from Belyi Island in the Kara Sea (West Siberian sector of Russian Arctic). The major types of soils predominating in the soil cover were sampled. The concentrations of trace elements (mgkg-1) varied within the following ranges: 119-561 for Mn, 9.5-126 for Zn, 0.082-2.5 for Cd, <0.5-19.2 for Cu, <0.5-132 for Pb, 0.011-0.081 for Hg, <0.5-10.3 for Co, and 7.6-108 for Cr; the concentration of Fe varied from 3943 to 37,899mgkg-1. The impact of particular soil properties (pH, carbon and nitrogen contents, particle-size distribution) on metal concentrations was analyzed by the methods of correlation, cluster, and factor analyses. The correlation analysis showed that metal concentrations are negatively correlated with the sand content and positively correlated with the contents of silt and clay fractions. The cluster analysis allowed separation of the soils into three clusters. Cluster I included the soils with the high organic matter content formed under conditions of poor drainage; cluster II, the low-humus sandy soils of the divides and slopes; and cluster III, saline soils of coastal marshes. It was concluded that the geomorphic position largely controls the soil properties. The obtained data were compared with data on metal concentrations in other regions of the Russian Arctic. In general, the concentrations of trace elements in the studied soils were within the ranges typical of the background Arctic territories. However, some soils of Belyi Island contained elevated concentrations of Pb and Cd.

Shear Resistance of Rubber-ballast Composites in Simulated Water and Acid Soaked Conditions

Ballast is one of the main structures for the railway tracks. It can resist the lateral movement under dynamic loading transferred by the passing trains with repeatedly. Under some circumstances, ballast can suffer degradation or breakdown due to the repeated loading and maintenance. Ballast is easily exposed to the weather because it is laid on the track. Acid rain affects the performance of the railway track near the industrial and urban area. As a result, it starts to foul and the small chips from ballast filled the void, as well as reduce the shear strength of ballast particles. This situation can contribute into the increasing of maintenance frequency and costing. This paper examines the potential of rubber inclusions in increasing the shear resistance of rubber-ballast composites in simulated water and acid soaked conditions with several configuration. This lab-based exploratory work is only static load simulation in conventional shear box setup measuring 60 mm × 60 mm. The aggregates size is 10 times smaller than actual size of ballast. In order to identify the shear resistance deterioration of rubber-aggregates mixture under poor drainage conditions by soaked a batch of aggregates in water and acid solution for 2 weeks to simulate accelerated weathering effects. The shear resistance did not rise dramatically with the rubber reinforcement. This susceptible shear strain plots indicate ductile behaviour on the aggregates-rubber composites. This is evident by the linear rise of shear stress with strain up to approximately 10% for the control samples (CS) until it reaches a constant value. Note that all the specimens including CS are in a loose state during the testing because there were no tamping been applied on the samples. Overall the circular patch (CP) specimen was the most favourable than the other configurations. Both mechanisms contributed to the reduced overall subsistence, accompanied by an increase in the shear resistance. The inclusion of rubber elements apparently prevented the dilation of the granular material when approaching the shear failure and the reducing the settlement.

Geomorphic Site Analysis to Study Soils Developed on a Toposequence of Schist Landform in Yadgir District of Karnataka

Three representative diversified pedons namely red, brown and black from the geomorphic units upper, middle and lower sectors, respectively in a toposequence on schist landscape were studied for their morphological, physical and chemical properties to understand the genesis and to classify as per USDA Soil Taxonomy. Red pedon was well drained as it recorded the highest (3) moist chroma and the drainage got poor down the slope in brown and black pedons where the moist chroma was 2 and 1, respectively. Dominant soil colour hue was 5YR in red pedon and 7.5 YR and 10 YR in brown and black pedons, respectively. Soil texture got finer down the slope and it was gravelly clay loam in red pedon and clay in both brown and black pedons. Clay skins, pressure faces and slickensides were observed in red, brown and black pedons, respectively. Chemical composition of fine sand fraction of pedons was almost same in all the pedons and CEC/clay, Feo/Fed and SiO2/Fe2O3 ratios showed increasing trend down the slope. The pedogenic processes associated with the upper sector member red pedon were leaching, decalcification, tendency of desilicification, laterization and kaolinization under well drained condition whereas, the middle and lower sector members brown and black pedons were formed by the pedogenic processes like calcification and silicification under poor drainage condition. Thus, a difference in drainage conditioned by topography is the important pedogenic factor in the genesis of diversified soils in a toposequence. At sub group level red, brown and black pedons were classified as Typic Haplustalfs, Vertic Haplustepts and Leptic Haplusterts, respectively.

English

Urban Land fill pavement drainage is one of the key components which need to be considered along with other parameters for urban land fill pavement management system. In which various issues related with integrating the urban land fill pavement roadway drainage with Land fill pavement Management System. It highlights the major ingress and egress routes of water in land fill pavement structure, methods to measure moisture and approaches to control the water entry. This paper reviews different software's for designing the drainage system and techniques for modeling the drainage conditions in land fill pavement deterioration models. The effect of poor surface and subsurface drainage on land fill pavement performance and its life-cycle are also discussed. The measures to manage the poor land fill pavement roadway drainage conditions are also presented. The need for a detailed field and laboratory studies related to land fill pavements drainage systems has been demonstrated.

Caracterização dos Solos e da Estrutura Fitossociológica da Vegetação de Veredas da Chapada no Triângulo Mineiro

As veredas se destacam como um sistema de drenagem superficial composto pela rede de drenagem com cursos d’água que ocupa os interflúvios largos dentro do domínio Cerrado. Nas Veredas os solos são formados sob condições de drenagem deficiente. Nestas condições há uma tendência para a formação de solos hidromórficos. Com o objetivo de investigar a importância e o uso dado para os recursos naturais das veredas pela população rural do município de Uberlândia-MG foram realizadas entrevistas com 20 proprietários rurais. As veredas apresentam-se como uma fonte de água de fácil acesso. Segundo os entrevistados as veredas possuem água de boa qualidade, para uso doméstico, salvo em condições de represamento onde a água adquire coloração amarelada, com presença de lodo avermelhado e sabor ferruginoso. A água para consumo humano, em sua maior parte é obtida de poços artesianos...Palavras-Chave: Veredas; Cerrado; Estudos Edáficos; Uberlândia.

Study on Prediction of the Final Soil Salinity for Soil Desalinization and the Amount of Reclamation Water Requirement for Salt Leaching of Saline and Sodic Soils Using Empirical Simulation Models (Case Study: Khuzestan Province, Iran)

The study area was located at central part of Khuzestan province, Iran. Soil survey and land classification of the area showed that from total surveyed area of about 41,855 hectares, an area of about 14,100 hectares (33.7%) were saline / saline - sodic soils, in different extents. Also about 36,430 hectares (87.0 % of the total area) was subjected to water logging and poor internal drainage conditions. To study the possibilities of Desalinization and Desodification, six different sites were selected in the most Saline – Sodic parts of the study area for which eight treatments (Six for leaching water applications and two with gypsum as soil amendment) by means of 1.0 meter depth of leaching water application in four 0.25 meter intervals. Soil samples were taken before, during and after each leaching water application interval. The collected soil and water samples were then analyzed in the laboratory. Based on the collected data from salt leaching experiments, the Desalinization and Desodification leaching curves were obtained. Different theoretical models were also tested by comparing the calculated and experimental Desalinization and Desodification data. Reasonable agreements between theoretical and typical experimental leaching curves were observed. Some empirical exponential relationships were then obtained, enabling users to insert leaching efficiency coefficient and volumetric soil water content and depths to predict both final soil salinity and sodicity along with required depth of leaching water application. Also, application of any amendment materials such as gypsum was not needed for the reclamation of these soils.

DEVELOPMENT OF PAVEMENT MANAGEMENT STRATEGIES FOR ARTERIAL ROADS

An arterial road is a high-capacity urban road whic h delivers the traffic from collector roads to free ways, and between city centres at the maximum and possible level of service. Therefor e it is very important to maintain these roads as t hey are subjected to heavy traffic and on monsoon or poor drainage conditions which ma y damage the pavements at a faster rate further req uiring timely maintenance and costly rehabilitation. Assessing the condition of the pavement periodically is important so that m aintenance work can be taken up accordingly in order to slow down the deterioration rate. A tool which can access the deterioration of pavement is a Pavement Condition Index (PCI) which is a distress study car ried out on pavement. PCI is a numerical rating of the pavement condition that ranges from 0 -100 with 0 being worst possible cond ition 100 being the best possible condition. Theref ore, this paper aims at bringing out the methodology used in carrying out the survey on the pavement and for rating of the pavement (PC I) with the case studies of four arterial roads of Rajarajeshwari Zone, Bangalo re city and the PCIs of rating of these pavements a t the time of studies was found to be from very poor to excellent. Pavement management strategies have been proposed based on the condition rating.

Hydrogeological conditions and aquifers potentiality for sustainable development of the desert areas in Wadi Qena, Eastern Desert, Egypt

To increase the potentiality of development and land reclamation activities, the Egyptian government funds the construction of a new desert road in Upper Egypt. This road connects Upper Egypt with the Red Sea Governorate. Surrounding the road is 207,000 acres of land surface which is almost flat and suitable for reclamation. To ensure the sustainability of the proposed development surrounding the road, analyses of the morphometric parameters, infiltration test and the grain size distribution, geoelectrical and hydrogeological investigations were conducted in the area. The results indicated a possibility of flash flood hazards and poor drainage condition for land reclamation activities is expected. The hydrogeological and geoelectrical investigations revealed that the unconfined Quaternary and confined Nubian Sandstone aquifers are the main aquifers in the area. The depths to water in the two aquifers range from 18 to 36 and 80 to 300 m with an average thickness of 40 and 275 m, respectively. The aquifers are made of sands and silt with clay intercalations. The total dissolved solids of water ranges between 1,700 and 5,400 mg/L, whereas the sodium absorption ratio ranges between 7 and 30 meq/L, indicating the suitability of water for irrigating medium- to high-salt-tolerant crops with proper drainage facilities. Thus, water in this area is not suitable for domestic use. Based on hydrogeological equations, the available water for extraction from the aquifers in the area is about 17.195 × 109 m3, and this volume is not feasible to reclaim the whole proposed area for reclamation. Meanwhile, it may be possible to water small farms (not more than 60,000 acres for 50 years). Surface water source should be considered for the sustainability development of the area.

Occurrence of well-crystallized Nontronite in the Gas Vesicles of a Megaporphyritic Basalt Flow near Nighoj, Ahmednagar district, Maharashtra

Abstract Occurrence of well crystallized nontronite in a megaporphyritic basalt flow from Nighoj area, Maharashtra, India is reported. Thin section studies of the vesicles from periphery to the centre reveal the presence of greenish palagonite, probably indicating the stages of devitrification of glass and the weathering of palagonite to the formation of nontronite. The centre of the vesicles is marked by the presence of dark greenish-brown, radiating and fibrous sheets of nontronite. X-ray diffraction (XRD) analysis reveals the dominant presence of smectite (nontronite) as the major phase with traces of pyroxene. Scanning Electron Microscopy (SEM) shows well developed sheets of nontronite within the gas vesicles of the megaporphyritic basalt flows. In the present investigation, the nontronite within the gas vesicles of the megaporphyritic basalts at Nighoj was formed in-situ due to the devitrification of glass containing palagonite. Palagonite is an intermediate step in the alteration that may be accomplished by the steam generated in quenching of the lava. Weathering of palagonite under conditions of poor drainage is essential to the genesis of nontronite as has been suggested by Victor and Vernon (1946).

Soil physico-chemical, mineralogical, and micromorphological changes due to desertification processes in Yazd region, Iran

Nine pedons and 30 surface samples were taken, described, and analyzed to investigate the effect of desertification on soil quality indices, mineralogical, and micromorphological properties of three regions (desert, semi-desert, non-desert) in central Iran. The results showed that moving from a non-desert to a desert area decreased soil quality indices such as organic matter (from 0.5% to 0.2 %) and microbial respiration (from 1.59 to 0.11 mgCO2 g−1 soil). By contrast, increases were recorded for bulk density (1.2 to 1.9 Mg m−3) and soil salinity (5 to 19 dS m−1). Soil in the non-desert area had a sandy texture that led to good drainage conditions, while soil in the desert area had a clayey texture that led to poor drainage conditions. The mineralogical assemblage of the soil was approximately the same for all the three areas, with illite and chlorite being the main minerals. Kaolinite and smectite were present in lower concentrations. The micromorphological evidence showed that the main microstructure of the non-desert region was granular, probably because of the higher organic matter content in this area. In the desert region, platy structure was abundant. Overall, a more thorough perception of the desertification process was gained by studying its impact on soil properties.

OPTIMUM GROUNDWATER TABLE DEPTH AND IRRIGATION SCHEDULES FOR CONTROLLING SOIL SALINITY IN CENTRAL IRAQ

ABSTRACTExcessive irrigation and poor drainage conditions are the major factors contributing to rising groundwater tables and soil salinity in the irrigated areas of Central Iraq. Therefore calculations of precise irrigation requirements are necessary to optimize crop production and keep the groundwater table below the root zone to avoid soil salinization. In this study, the soil–water–atmosphere–plant (SWAP) model is used to determine optimal groundwater table depth and irrigation amounts for the study area. SWAP was calibrated using field data from the study area during the wheat and maize season of 2011–2012. The modelling results reveal that under current irrigation practices (600 mm to wheat and 1000 mm to maize), more than 30% water is lost as deep percolation. This causes a rise in the groundwater table and reduction in crop yields. The model simulations suggest that a groundwater table depth of 200 cm together with an irrigation application of 500 mm to wheat and 600 mm to maize will be the best combination to attain optimal yields. Therefore a drainage system in these areas should be installed to maintain groundwater table depth around 200 cm. Maintaining adeeper groundwater table will not be suitable as costs will increase and crop responses negligible. For long‐term sustainability, rehabilitation of existing drainage systems to evacuate excessive salts from the root zone will be imperative. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Spatial variability of some soil properties: a case study of the Lower Seyhan river basin inTurkey

The aim of this study was to evaluate the performance of a closed drainage system in one area of the Lower Seyhan river basin in Cukurova, Turkey by measuring spatial variations in soil characteristics. Seven parallel transects which had a 150 m length were selected at 5 m intervals within the study area, and 104 soil samples were collected and analysed for soil pH, electrical conductivity (EC), exchangeable sodium (Na) content and exchangeable sodium percentages (ESP). Results were subjected to inverse distance weighting (IDW) interpolation. EC, pH and ESP estimates obtained from IDW interpolation were compatible with the results of soil analysis. Cross validation was performed to determine the accuracy of the interpolation technique. Interpolation of EC values showed a high mean error in 120–150 cm depth (9.010%), which was attributed to poor drainage conditions. Minimum sample number, maximum sample number, maximum radius and power were found to have an influence on the accuracy of IDW interpolation. ESP, exchangeable Na, EC values were generally low for shallow soil horizons, with values increasing with increases in depth. Data sets were analyzed with two-way ANOVA (the factors were six pipe regions (1–6) and five soil depths (30, 60, 90, 120, 150 cm)) and means compared with Duncan’s multiple range test. It was found that the efficiency of drainage pipe, in regions 1, 2, 3 and 4 can diminish rather than the other pipe regions.

DRAINAGE PERFORMANCE ASSESSMENT IN A MODERNIZED OASIS SYSTEM

ABSTRACTSaharan oases are frequently subjected to waterlogging due to the presence of shallow and salty groundwater and poor irrigation and drainage conditions. To overcome this problem in Tunisia, in 2002 an official modernization programme was implemented based on two operations: (i) increasing irrigation efficiency by building concrete irrigation canals to limit losses due to water percolation and (ii) controlling waterlogging and salinity by installing a subsurface drainage system in place of the traditional open‐ditch system. In this study, a salinity balance was performed in Fatnassa, a representative Saharan oasis in Tunisia. Two spatial levels were monitored over a period of two years: an irrigated and drained field (0.8 ha) and the northern part of the oasis covering 114 ha. Results showed an equilibrated salinity balance at the field level, whereas, at the oasis level, the drainage system was unable to evacuate more than 30% of the salts in the first year and 15% in the second. We consider the clogging effect detected in several locations in the oasis as the main cause of this dysfunction. For the future, we recommend a more participatory approach to designing drainage systems, probably moving toward mixed systems with traditional open ditches and modern subsurface pipes, both easy to maintain by the farmers themselves. Adequate envelopes to prevent clogging in mineral soils have to be tested in situ before extension of subsurface drainage. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Estimating Contributions of Nitrate and Herbicides From Groundwater to Headwater Streams, Northern Atlantic Coastal Plain, United States1

Abstract: Groundwater transport often complicates understanding of surface‐water contamination. We estimated the regional flux of nitrate and selected herbicides from groundwater to nontidal headwater streams of the Atlantic Coastal Plain (New Jersey through North Carolina) based on late‐winter or spring base‐flow samples from 174 streams. Sampled streams were selected randomly, and flux estimates are based on resulting population estimates rather than on empirical models, which have been used previously for similar estimates. Base‐flow flux in the estimated 8,834 headwater streams of the study area are an estimated 21,200 kg/day of nitrate (as N) and 5.83, 0.565, and 20.7 kg/day of alachlor, atrazine, and metolachlor (and selected degradates), respectively. Base‐flow flux of alachlor and metolachlor is &lt;3% of the total base‐flow flux of those compounds plus degradates. Base‐flow flux of nitrate and herbicides as a percentage of applications is typically highest in well‐drained areas and lowest in areas with abundant poor drainage and anoxic conditions. In Coastal Plain watersheds of Albemarle and Pamlico Sounds, &lt;2% of applied nitrogen reaches headwater streams as base flow. On the Delmarva Peninsula part of the Chesapeake Bay watershed, however, more than 10% of such applications are transported through groundwater to streams, and base‐flow nitrate flux represents 70% of total nitrogen flux in headwater streams.