scholarly journals Transmissivity and groundwater flow exert a strong influence on drainage density

2021 ◽  
Author(s):  
Elco Luijendijk
Keyword(s):  
Groundwater Flow ◽  
Overland Flow ◽  
Landscape Evolution ◽  
Drainage Density ◽  
Initial Slope ◽  
Humid Climate ◽  
Climate Conditions ◽  
Stream Incision ◽  
Strong Control ◽  
Stream Erosion

Abstract. The extent to which groundwater flow affects drainage density and erosion has long been debated, but is still uncertain. Here, I present a new hybrid analytical and numerical model that simulates groundwater flow, overland flow, hillslope erosion and stream incision. The model is used to explore the relation between groundwater flow and the incision and persistence of streams for a set of parameters that represent average humid climate conditions. The results show that transmissivityand groundwater flow exert a strong control on drainage density. High transmissivity results in low drainage density and high incision rates and vice versa, with drainage density varying roughly linearly with transmissivity. The model evolves by a process that is defined here as groundwater capture, whereby streams with a higher rate of incision draw the watertable below neighbouring streams, which subsequently run dry and stop incising. This process is less efficient in models with low transmissivity due to the association of low transmissivity and high watertable gradients. A comparison of different parameters shows that drainage density is the most sensitive to transmissivity, followed by parameters that govern initial slope and stream erosion. These results imply that permeability and transmissivity exert a strong control on drainage density, stream incision and landscape evolution and that models of landscape evolution may need to explicitly include groundwater flow.

scholarly journals Transmissivity and groundwater flow exert a strong influence on drainage density

2022 ◽  
Vol 10 (1) ◽  
pp. 1-22
Author(s):  
Elco Luijendijk
Keyword(s):  
Groundwater Flow ◽  
Water Table ◽  
Overland Flow ◽  
Landscape Evolution ◽  
Drainage Density ◽  
Initial Slope ◽  
Humid Climate ◽  
Climate Conditions ◽  
Stream Incision ◽  
Strong Control

Abstract. The extent to which groundwater flow affects drainage density and erosion has long been debated but is still uncertain. Here, I present a new hybrid analytical and numerical model that simulates groundwater flow, overland flow, hillslope erosion and stream incision. The model is used to explore the relation between groundwater flow and the incision and persistence of streams for a set of parameters that represent average humid climate conditions. The results show that transmissivity and groundwater flow exert a strong control on drainage density. High transmissivity results in low drainage density and high incision rates (and vice versa), with drainage density varying roughly linearly with transmissivity. The model evolves by a process that is defined here as groundwater capture, whereby streams with a higher rate of incision draw the water table below neighbouring streams, which subsequently run dry and stop incising. This process is less efficient in models with low transmissivity due to the association between low transmissivity and high water table gradients. A comparison of different parameters shows that drainage density is most sensitive to transmissivity, followed by parameters that govern the initial slope and base level. The results agree with field data that show a negative correlation between transmissivity and drainage density. These results imply that permeability and transmissivity exert a strong control on drainage density, stream incision and landscape evolution. Thus, models of landscape evolution may need to explicitly include groundwater flow.

Modelling the effects of permeability, groundwater flow and water table depth on landscape evolution

2020 ◽  
Author(s):  
Elco Luijendijk
Keyword(s):  
Groundwater Flow ◽  
Overland Flow ◽  
Landscape Evolution ◽  
Drainage Density ◽  
Stream Channels ◽  
Erosion Rates ◽  
Landscape Models ◽  
Storage Term ◽  
Stream Erosion

<p>The role of groundwater flow in determining overland flow, drainage density and landscape evolution has long been debated. Landscape models often only address groundwater as a simplified storage term and do not explicitly include lateral groundwater flow, although recently some model codes have started to include lateral flow. However, the role of groundwater flow on landscape evolution has not been explored systematically to my knowledge. Here I present a new numerical and analytical model that combines groundwater flow, saturation overland flow, hillslope diffusion and stream erosion. A number of model experiments were run with different values of transmissivity and groundwater recharge. The model results demonstrate that transmissivity, groundwater flow and the depth of the watertable strongly govern overland flow, the incision of stream channels and erosion rates. The results imply that the permeability and transmissivity of the subsurface are important parameters for explaining and modelling landscape evolution.  </p>

Sewage Treatment in Helophyte Beds–First Experiences with a New Treatment Procedure

1987 ◽  
Vol 19 (10) ◽  
pp. 1-10 ◽  
Author(s):  
K. Bucksteeg
Keyword(s):  
Waste Water ◽  
Rural Areas ◽  
Root Zone ◽  
Waste Water Treatment ◽  
Sewage Treatment ◽  
Uptake Capacity ◽  
Humid Climate ◽  
Climate Conditions ◽  
Trickling Filters ◽  
Operation Conditions

Waste water treatment in helophyte beds under humid climate conditions has been favoured by some German ecologists for some years. The idea is to cause waste water to flow horizontally through the root zone of helophytes to achieve satisfactory effluent properties. There exist many highly different proposals regarding the choice of soil and helophytes to be applied, bed area, design of inlets and outlets and operation conditions. A few plants have been operated in practice for some years. It appears that clogging is one of the main problems occurring in these plants. The hydraulic uptake capacity of soil is discussed in Darcy's law. Comparisons with observations of plants in operation are drawn. The interactions between soil properties, its uptake capacity, BOD5-, COD-, N- and P-reduction are evaluated. The effluent results of helophyte beds are compared with those of low-loaded trickling filters and of ponds used for sewage treatment in small villages in rural areas of Germany. It has been proved that the total construction costs of sewage treatment plants with helophyte beds used as the biological stage are higher when compared with those of conventional plants in general.

scholarly journals Incipient subsurface heterogeneity and its effect on overland flow generation – insight from a modeling study of the first experiment at the Biosphere 2 Landscape Evolution Observatory

2014 ◽  
Vol 18 (5) ◽  
pp. 1873-1883 ◽  
Author(s):  
G.-Y. Niu ◽  
D. Pasetto ◽  
C. Scudeler ◽  
C. Paniconi ◽  
M. Putti ◽  
...  
Keyword(s):  
Null Hypothesis ◽  
Overland Flow ◽  
Landscape Evolution ◽  
Alternative Hypothesis ◽  
Biosphere 2 ◽  
Subsurface Heterogeneity ◽  
Flow Generation ◽  
Heterogeneous Soil ◽  
Seepage Face ◽  
Modeling Study

Abstract. Evolution of landscape heterogeneity is controlled by coupled Earth system dynamics, and the resulting process complexity is a major hurdle to cross towards a unified theory of catchment hydrology. The Biosphere 2 Landscape Evolution Observatory (LEO), a 334.5 m2 artificial hillslope built with homogeneous soil, may have evolved into heterogeneous soil during the first experiment driven by an intense rainfall event. The experiment produced predominantly seepage face water outflow, but also generated overland flow, causing superficial erosion and the formation of a small channel. In this paper, we explore the hypothesis of incipient heterogeneity development in LEO and its effect on overland flow generation by comparing the modeling results from a three-dimensional physically based hydrological model with measurements of total mass change and seepage face flow. Our null hypothesis is that the soil is hydraulically homogeneous, while the alternative hypothesis is that LEO developed downstream heterogeneity from transport of fine sediments driven by saturated subsurface flow. The heterogeneous case is modeled by assigning saturated hydraulic conductivity at the LEO seepage face (Ksat,sf) different from that of the rest (Ksat). A range of values for Ksat, Ksat,sf, soil porosity, and pore size distribution is used to account for uncertainties in estimating these parameters, resulting in more than 20 000 simulations. It is found that the best runs under the heterogeneous soil hypothesis produce smaller errors than those under the null hypothesis, and that the heterogeneous runs yield a higher probability of best model performance than the homogeneous runs. These results support the alternative hypothesis of localized incipient heterogeneity of the LEO soil, which facilitated generation of overland flow. This modeling study of the first LEO experiment suggests an important role of coupled water and sediment transport processes in the evolution of subsurface heterogeneity and on overland flow generation, highlighting the need of a coupled modeling system that integrates across disciplinary processes.

scholarly journals An Investigation of Design Considerations to Achieve Thermal Comfort in Warm Humid Climatic Zone of West Bengal

2021 ◽  
Vol 9 (11) ◽  
pp. 1912-1917
Author(s):  
Pritam Roy
Keyword(s):  
Thermal Comfort ◽  
Building Materials ◽  
West Bengal ◽  
Building Design ◽  
Climatic Zone ◽  
Primary Study ◽  
Humid Climate ◽  
Climate Conditions ◽  
Building Orientation ◽  
Design Factors

Abstract: This research paper presents the investigation of design consideration to achieve thermal comfort and the warm humid climatic zone of West Bengal is considered as the primary study area for the investigation. The varying thermal comfort behavior of humans in different climate conditions and seasons clearly demonstrates that the building design strategy must conform with the region of the building. In this paper, first studying the climatic characteristics of the warm humid region design factors are selected like building materials, cross ventilation, building orientation, roofing orientation, and materials, etc. After that, all those design factors are studied and the effect of all those factors on building in various conditions is observed. Keywords: Warm Humid Climate, Thermal Comfort, Building Materials, U-value, Cross Ventilation, Building Orientation

scholarly journals Investigation of climate change and history of lead deposition using soil archives

2008 ◽  
Vol 72 (1) ◽  
pp. 341-343 ◽  
Author(s):  
T. Pampura ◽  
V. Demkin ◽  
A. Probst
Keyword(s):  
Climate Change ◽  
Middle Ages ◽  
Isotopic Ratios ◽  
Humid Climate ◽  
Climate Conditions ◽  
Anthropogenic Lead ◽  
Significant Difference ◽  
Profile Distribution ◽  
History Of ◽  
Burial Mounds

AbstractOur study focused on the investigation of climate change and the fate of lead in soils from the Low Volga region of Russia over 3500 years. We used a comparative analysis of the modern soils and palaeosols preserved under burial mounds, which date back to the Middle Ages and the Early Iron and Bronze Ages. A climate reconstruction showed periodic changes, with the most humid climate conditions occurring during Golden Horde period. However, we could not find any consistent changes in Pb concentration and profile distribution following the climate change. We observed a clear difference in Pb isotopic ratios between the lower and upper horizons both for the modern and buried profiles, reflecting the influence of atmospheric lead depositions. However, there is no statistically significant difference in Pb isotopic ratios between the upper horizons of buried and modern soils (except modern soils collected in the vicinity of a motorway). This means that either anthropogenic input due to long range air transport was insignificant, or that airborne anthropogenic lead and natural airborne lead have similar isotopic composition.

Response of selected water chemical quality parameters to slight thinning in a mature oak–beech forest ecosystem under sub-humid climate conditions

2017 ◽  
Vol 136 (4) ◽  
pp. 653-664 ◽  
Author(s):  
Ibrahim Yurtseven ◽  
Ferhat Gökbulak ◽  
Yusuf Serengil ◽  
Betül Uygur Erdoğan ◽  
Mehmet Said Özçelik ◽  
...  
Keyword(s):  
Forest Ecosystem ◽  
Beech Forest ◽  
Quality Parameters ◽  
Chemical Quality ◽  
Humid Climate ◽  
Climate Conditions

A Drought Warning System for Thailand

2005 ◽  
Author(s):  
Apisit Eiumnoh ◽  
Rajendra P. Shrestha
Keyword(s):  
Agricultural Land ◽  
Warning System ◽  
Drainage Density ◽  
Agricultural Economics ◽  
Severe Drought ◽  
Humid Climate ◽  
Moderate Drought ◽  
Hot Season ◽  
Agricultural Use ◽  
Dry Climates

Thailand is located between 5°30' and 20°30'N latitudes and between 97°30' and 105°30'E longitudes. Geographically, the country can be divided into northern, northeastern, central, and southern regions. Most of the country experiences distinct wet and dry climates, except some parts of the southern region, which experience a wet and humid climate. Of the country’s total area (514,000 km2), 41% is under agricultural use (Office of Agricultural Economics, 1999) with 92% of it being rainfed. Drought normally occurs during the hot season (March–April) and sometimes during dry season (November–April) due to inadequate rains. In recent times, the occurrence of drought has increased in Thailand, threatening sustainability of agricultural production. According to Department of Local Administration (1998), droughts of varying intensity occur in 67 out of 76 provinces of Thailand almost every year. During the period from 1987 to 1997, drought impacted a total of 5.44 million ha of agricultural land, causing $1.4 billion in losses. Droughts of varying intensity or severity occur in different regions of Thailand. A drought is categorized as severe, moderate, slight, or none drought using a radiative index (RI) determined during the rainy season (May– October). The RI for a region is determined using the number of rainy days, percentage of irrigated area, groundwater availability, topography, land use, soil, drainage density, and watershed size. If RI ranges from 1.0 to 1.2 for 15 consecutive days for a region or area, the region is said to be affected by slight drought. If RI exceeds 1.2 for 30 consecutive days, the region is considered to be affected by moderate drought, and if RI exceeds 1.0 for more than 30 consecutive days, severe drought is said to have occurred in the region. Using these criteria, the percentage of area affected by different drought categories has been determined in Thailand. It can be observed from table 25.1 that the northeastern region is the most droughtprone in Thailand. A drought index, D, is also used to monitor drought conditions in Thailand.

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