Circular Pond Research Articles

Use of Tension Infiltrometer Data with Unsaturated Hydraulic Conductivity Models

AbstractA new method is presented to estimate the relationship between unsaturated hydraulic conductivity and soil‐water pressure using tension infiltrometer data. In this method, both the early transient and the subsequent quasi‐steady stages of the infiltration process underneath a tension infiltrometer disc are analyzed. Our investigation indicates that the infiltration rate at early times closely follows the aquare‐root‐of‐time relationship (Philip, 1969). This behavior permits the evaluation of the sorptivity, which is an integrated measure of soil diffusivity. At later times, three‐dimensional quasi‐steady flow beneath the infiltrometer disc develops, and the Wooding equation for flow from a circular pond is used to evaluate the sorptive number and the saturated hydraulic conductivity. Simple algebraic expressions are introduced to relate the sorptivity and sorptive number to the parameters of the Brooks and Corey model of unsaturated hydraulic conductivity. The method described here extends the utility of tension infiltrometer data to a large class of hydraulic conductivity models and provides an in situ technique to determine suitable parameters values for these models.An ICP‐MS, equipped with an ultrasonic nebulizer and active‐film multiplier detector, is used to attempt to determine 54 trace elements directly in ground water. Lithium, arsenic, rubidium, strontium, barium, and antimony are found in the microgram‐per‐liter (part‐per‐billion = ppb) range. Most of the other elements are present at nanogram‐per‐liter (part‐per‐trillion = ppt) concentrations. Ion exchange preconcentration is utilized in order to improve the sensitivity for measuring the rare earth elements that exist at concentrations as low as 0.05 ppt for lutetium, thulium, and terbium. The formation of molecular species in the plasma produces false positive results for some of the elements. The presence of silicon or carbon dioxide interferes with the measurement of scandium, strontium interferes with rhodium and palladium, and barium interferes with europium. Correction procedures for these interferences are discussed. All together, the concentrations of the 54 elements in water from four Nevada springs span almost seven orders of magnitude.

Two‐ and three‐dimensional steady quasi‐linear infiltration from buried and surface cavities using boundary element techniques

A general numerical method is presented for solving the problem of quasi‐linearized steady infiltration from general two‐dimensional and axisymmetric surface cavities and from a general cavity buried at an arbitrary depth in either a two‐ or three‐dimensional semi‐infinite porous medium. Numerical results are compared with known analytical results for the cases of a shallow circular pond and a circular cylindrical cavity and a spherical cavity buried in an infinite medium. Further results are presented graphically illustrating the effect of an upper surface on the flux from a circular cavity and also the effect on the size of the effective wetted region. Two‐dimensional surface cavities are also investigated, and the dependence of the flux on geometry, gravity, and capillarity is examined.

Seepage from channels and ponds with impervious boundary walls extending below floor level

The steady-state seepage after long times from flat-bottomed channels into “Green and Ampt” type soils is analysed using the method of conformal transformations for the case of an impervious boundary wall extending below floor level. Relationships, expressed in dimensionless form, are given showing the dependence of the seepage rate on the depth of the boundary wall and soil hydraulic properties. Similar relationships, obtained by an electric analogue that approximated to the hydraulic situation, are presented for the case of a circular pond with an impervious boundary wall. These relationships are useful not only for estimating the seepage from channels and reservoirs but also for analysing results from infiltrometer rings.

Comparing a three-dimensional and a Dupuit-Forchheimer solution for a circular recharge area in a confined aquifer

An exact, closed-form analytic solution is presented for three-dimensional steady-state flow due to a source disc. The solution is used to model a circular recharge area at the upper boundary of a confined aquifer. Streamlines and contour plots of equipotentials are compared with those obtained from a Dupuit-Forchheimer solution. The latter solution is approximate in that resistance to vertical flow is ignored. As a further illustration a groundwater contamination problem is solved; that of a leaching circular pond in a uniform flow field. Some streamlines and the shape of the downstream plume are plotted for both the three-dimensional and the Dupuit-Forchheimer solution. It appears that when the recharge area is sufficiently large the Dupuit-Forchheimer solution is quite adequate, particularly when tracing streamlines. The results, therefore, confirm the validity of the Dupuit-Forchheimer assumption when modeling regional flow, even under circumstances of areal recharge. However, when the size of the recharge area is in the order of the aquifer thickness a truly three-dimensional solution is needed.

Steady infiltration from small shallow circular ponds

R. A. Wooding's (1968) analysis of steady infiltration from a shallow circular pond is reviewed and extended. A new approximation is obtained for the total steady flow of water into the soil from ponds with small radii. The main result is the approximation F* = 4π sin2a/{aπ sin a cos a + 2a sin 2 a ln a − a3[1 + 2ψ(3/2;)]}, which is accurate to within 2% for a less than 0.4. Here F* approximates the dimensionless flow from the pond, and a is the usual dimensionless pond radius. This result may be significant to ring infiltrometers, since substantial errors in estimates for apparent soil properties result for moderate values of a if the accurate approximation F* is replaced by the well‐known approximation 4 + 2πa. The presence of a logarithmic term in this expansion indicates that flows from surface sources have a different analytic structure than those from buried sources.

Simple Low-Cost Circular Ponds

Abstract Simple, inexpensive circular ponds were constructed with galvanized sheet iron sides on a concrete base. Construction details are described.

Pingos in Northernmost Sweden

Ice-cored mounds in a small area in northernmost Sweden are briefly described. The morphological features include hummocks, interpreted as pingos, more palsa-like mounds and fossil forms in the shape of circular ponds. Drilling in one hummock revealed a massive ice core covered by fine grained sediment and glacial till. The sediment is slightly organic and probably of interglacial age. A number of mounds appear to have subsided during the last two decades and no signs of growth have been observed during the same period. The subsidence is assumed to be climatically induced.

Numerical solutions to some free surface flows through nonhomogeneous media

AbstractSteady‐state, free surface seepage through a heterogeneous porous medium underlain by a drain at a finite depth is solved using a fixed domain solution technique. The problems investigated are axisymmetric seepage from a circular pond and plane seepage from a symmetric channel. These ponds and channels may have variable shaped bottoms. Since the Baiocchi transformation was used to define a new dependent variable, the form of the permeability function was restricted to a product of functions of the independent variables. Herein the permeability was chosen to be a function of the depth only. For certain forms of this function, namely those having negative gradients, part of the flowfield becomes unsaturated and this violates the assumed saturation of the flowfield in the flow theory. The governing differential equation, which holds in the sense of distributions, is derived for a fixed solution domain and a simple algorithm (a finite difference successive over‐relaxation scheme with projection) is given to obtain the solution to these free surface problems. Numerous comparisons are made with published results. Rigorous mathematical justification of the methods used herein can be found in the references cited.

Constant‐Flux Infiltration from a Hemispherical Cavity

AbstractExisting theories of Raats, Parlange, and Warrick describing constant‐flux absorption and infiltration from hemispherical cavities are reviewed. A simple theory for absorption is derived, using the flux‐concentration relation of Philip. Three‐dimensional infiltration experiments are described that were used to test these theories. The results showed that infiltration at 360 ml/h into a 4‐mm‐radius hemispherical cavity in a repacked fine sand was described quite well by the simple absorption theory for the first 100 min. Beyond this time, at this flux, the effects of gravity became evident, as expected from a comparison of the matric and gravitational potential gradients. The nonlinear, steady‐state infiltration theory of Raats gave reasonable estimates of the water content profiles behind the wet front. The linearised (constant diffusivity) theory of Warrick was of no value in this context. The success of the Raats theory adds some credence to the use in trickle irrigation design of the Wooding's theory which describes infiltration from a circular pond on the basis of the same assumptions.

Measuring saturated hydraulic conductivity and sorptivity using twin rings

A method of measuring, with minimal soil disturbance, the saturated hydraulic conductivity and sorptivity of field soil is presented and discussed. It involves measuring the steady-state infiltration of ponded water from two rings, of different radii, that have been lightly pressed into the soil surface. The method is based on Wooding's solution for steady infiltration from a shallow, circular pond. Criteria for selecting ring radii are discussed. Results for three field soils are found to give consistent values for the conductivity and sorptivity.

A bacterium with similarities to the redmouth bacterium and Serratia liquefaciens (Grimes and Hennerty) causing mortalities in hatchery reared salmonids in Australia

Abstract. Blood spots in the eye and haemorrhages in the musculature of the caudal peduncle were the main indication of disease in Australian hatchery reared brook trout Salvelinus fontinalis (Mitchill) and Atlantic salmon Salmo salar L. Mortalities of 0·1‐0·5% per day occurred for 3–4 weeks in fish stocked in circular ponds in the months of February and March when temperatures were falling from 23–11·C. The bacterium belonging to the Family Enterobacteriaceae had similarities with Yersinia ruckeri (the RM bacterium) and Serratia liquefaciens. As a temporary designation SBS was used. It is recommended that its taxonomic position remain sub judice for the present. Inoculation experiments on brook trout and landlocked Atlantic salmon indicated that signs appeared 2–7 days after inoculation and that rainbow trout Salmo gairdneri Richardson were resistant to the disease.

Rotator for Protecting Circular Fish Ponds against Predatory Birds

Rotator for Protecting Circular Fish Ponds against Predatory Birds

Infiltration from a Trickle Source: I. Mathematical Models

AbstractTheoretical considerations and mathematical tools to analyze multidimensional transient infiltration from a trickle source have been developed. Two mathematical models were considered: (i) a plane flow model involving the Cartesian coordinates x and z; and (ii) a cylindrical flow model described by the cylindrical coordinates r and z. The diffusion‐ type water flow equation in unsaturated soil was solved numerically by an approach that combines the noniterative ADI difference procedure with Newton's iterative method. The numerical results have been compared with Wooding's solution for steady infiltration from a circular pond and with a simple one‐dimensional solution. These comparisons indicate that the method is reliable and can be used with confidence. Typical results are demonstrated to show the effect of trickle discharge on the water content field, the saturated water entry zone, and the water flux at the soil surface.

Steady Infiltration from a Shallow Circular Pond

Steady infiltration from a shallow, circular, inundated area on the horizontal surface of a semi‐infinite porous medium is treated by a method of linearization proposed by J. R. Philip. Using this method, Philip retains most of the properties of the nonlinear system but reduces the differential equation to a linear type governing steady diffusion in a steady uniform flow. On the surface of the medium, the boundary conditions are of mixed type, although linear. These conditions are reduced to a system of dual integral equations solved by a modification of Tranter's method. Expressions for the distributions of vertical flux density, moisture content, and Stokes' stream function are derived, and numerical values of the last two quantities are illustrated graphically. It is found that the total flux depends almost linearly upon a parameter α, defined as the logarithmic derivative of the hydraulic conductivity with respect to capillary potential. Curves of mean flux over various radii (fractions of the total source radius) for various values of α indicate the importance of the guard ring in infiltrometer design.

Comparison of the Growth Rates of Chinook Salmon Fingerlings Reared in Circular Tanks and Foster-Lucas Ponds

Comparison of the Growth Rates of Chinook Salmon Fingerlings Reared in Circular Tanks and Foster-Lucas Ponds

Zinc Poisoning in a Trout Hatchery

Natural acid waters will dissolve zinc from galvanized-iron pipes. In some acid waters with a very low mineral content 0.01 p.p.m. dissolved zinc is toxic to brown and rainbow trout ova and alevins. All stages in the life history of rainbow trout are more susceptible to zinc poisoning than corresponding stages of brown trout. The lethal concentration normally decreases with the age of the fish, but considerable variations have been recorded amongst ova, aievins, fry, and fingerlings. Survivors from batches of fish subjected to dissolved zinc are less susceptible to further toxic concentrations than are specimens that have not previously been in solutions of zinc. Under certain conditions mortality amongst trout fingerlings, due to einc poisoning, will occur after they have been in a zinc vessel for 15 min. The effects of zinc poisoning may not be immediately apparent. When removed from zinc-contaminated to relatively zinc-free water trout may appear normal but death may occur within 48 hr. In well-aerated water, little or no flow is necessary for the development of trout ova, which will develop normally in distilled water. Aluminium paint does not normally protect an underlying metal from the action of acid water. Zinc is an unsuitable material for use in a hatchery with an unbuffered water supply. The lethal temperatures for acclimatized brown (Salmo trutta L.) and rainbow (Salmo gairdnerii Richardson) trout fingerlings in Victoria are 20–30°C. For adult fish the temperatures are 27–29°C. A self-cleaning hatchery inlet screen and a spray jet for circular ponds are described. In hot cliaates the temperature of water entering a pond through a spray jet is less than that of water entering through a normal radial-arm jet.

Salmon and Eel Movement in Constant Circular Current

Underyearling salmon in a circular pond of moving water at 20–25 °C. swam during the day and rested on the bottom at night. Before feeding they translocated actively upstream in rapid shallow water and in all directions in slow deep water. During feeding they held position in slow water, but made short excursions to seize food. After feeding, most moved into rapid, shallow water, the largest into the most rapid water.Translocating salmon usually went upstream and swam faster in more rapid water so that the rate of translocation remained constant. The rate of translocation increased with the size of the fish, more than doubling from 3 to 4 cm. in length.While steady illumination caused the salmon to swim up in the water from the bottom, a sudden change in light intensity when they were swimming, as by an object moving against the sky, caused them to swim quickly from shallow to deep water.Eels translocated upstream regularly only in the more rapid water, the swimming rate increasing with current rate. Eels 7 cm. long translocated almost twice as rapidly as salmon 3.5 cm. long. Eels burrowed in the gravel in bright daylight, came out in the evening and translocated rapidly even at night when the salmon were resting.

A Circular Pond with Central Outlet for Rearing Fry and Fingerlings of the Salmonidae

A Circular Pond with Central Outlet for Rearing Fry and Fingerlings of the Salmonidae