Infiltration Rates of Rainwaters in Sri Lanka Measured by Using Tritium Tracer

1982 ◽  
Vol 13 (1) ◽  
pp. 13-26 ◽  
Author(s):  
J. K. Dharmasiri ◽  
K. G. Dharmawardena ◽  
M. W. P. Wijesinghe ◽  
P. Thiranagama ◽  
I. D. T. De Mel ◽  
...  
Keyword(s):  
Sri Lanka ◽  
Soil Cover ◽  
Surface Soil ◽  
Infiltration Rate ◽  
Moisture Movement ◽  
Depth Profiles ◽  
Infiltration Rates ◽  
Central Highland ◽  
Piston Flow ◽  
Very High

Tritium tracer, injected below the surface soil, is used to follow the movement of soil moisture in the unsaturated zone at several geo-hydrologically different sites in Sri Lanka. Depth profiles of tritium activity and moisture contents have been measured after rainfall. For two well-established aquifers, Vanathavillu and Mannar, the recharge to groundwater is close to 30% of the rainfall. Infiltration is much higher. The moisture movement is apparently like piston flow. In the central highland regions, where the surface cover is composed of an overburden of fractured rocks overlain by a few metres of soil cover, the infiltration rate is very high.

INFILTRATION INTO HOMOGENEOUS AND LAYERED COLUMNS OF AGGREGATED LOAM, SILT LOAM, AND CLAY SOIL

1966 ◽  
Vol 46 (3) ◽  
pp. 293-305 ◽  
Author(s):  
W. J. Staple ◽  
R. P. Gupta
Keyword(s):  
Clay Soil ◽  
Aggregate Size ◽  
Infiltration Rate ◽  
High Variability ◽  
Silt Loam ◽  
Moisture Movement ◽  
Marked Influence ◽  
Infiltration Rates ◽  
Dry Soil ◽  
Moisture Profiles

Infiltration rates and moisture profiles were measured during vertical infiltration into three soils of differing texture and aggregate structure. The measurements were made both for homogeneous columns of the air-dry soil and for columns made up of two-layer combinations of the three soils. Infiltration rates and profiles for the same soils were computed on the basis of tension, diffusivity and conductivity data obtained on wetting. Agreement between measured and computed moisture profiles was satisfactory considering the high variability in moisture movement found in packed columns of coarsely aggregated soils. Differences in aggregate-size distribution and bulk density produced variation in tension and conductivity which in turn had a marked influence on infiltration rate.

The agronomic effectiveness of reactive phosphate rocks 1. Effect of the pasture environment

1997 ◽  
Vol 37 (8) ◽  
pp. 921 ◽  
Author(s):  
P. W. G Sale ◽  
R. J. Gilkes ◽  
M. D. A. Bolland ◽  
P. G. Simpson ◽  
D. C. Lewis ◽  
...  
Keyword(s):  
North Carolina ◽  
Phosphate Rock ◽  
Surface Soil ◽  
Annual Rainfall ◽  
Triple Superphosphate ◽  
Agronomic Effectiveness ◽  
P Sorption ◽  
Reactive Phosphate ◽  
Reactive Phosphate Rock ◽  
Very High

Summary. The agronomic effectiveness of directly applied North Carolina reactive phosphate rock was determined for 4 years from annual dry matter responses at 26 permanent pasture sites across Australia as part of the National Reactive Phosphate Rock Project. Fertiliser comparisons were based on the substitution value of North Carolina reactive phosphate rock for triple superphosphate (the SV50). The SV50 was calculated from fitted response curves for both fertilisers at the 50% of maximum yield response level of triple superphosphate. The reactive phosphate rock was judged to be as effective as triple superphosphate in the 1st year (and every year thereafter) at 4 sites (SV50 >0.9), and was as effective by the 4th year at 5 sites. At another 9 sites the reactive phosphate rock was only moderately effective with SV50 values between 0.5 and 0.8 in the 4th year, and at the final 8 sites it performed poorly with the 4th year SV50 being less than 0.5. Pasture environments where the reactive phosphate rock was effective in the 1st year were: (i) those on sandy, humic or peaty podsols with an annual rainfall in excess of 850 mm; (ii) those on soils that experienced prolonged winter inundation and lateral surface flow; and (iii) tropical grass pastures in very high rainfall areas (>2300 mm) on the wet tropical coast on North Queensland. The highly reactive North Carolina phosphate rock became effective by the 4th year at sites in southern Australia where annual rainfall exceeded 700 mm, and where the surface soil was acidic [pH (CaCl2) <5.0] and not excessively sandy (sand fraction in the A1 horizon <67%) but had some phosphorus (P) sorption capacity. Sites that were unsuitable for reactive phosphate rock use in the medium term (up to 4 years at least) were on very high P-sorbing krasnozem soils or high P-sorbing lateritic or red earth soils supporting subterranean-clover-dominant pasture, or on lower rainfall (< 600 mm) pastures growing on soils with a sandy A1 horizon (sand component >84%). No single environmental feature adequately predicted reactive phosphate rock performance although the surface pH of the soil was most closely correlated with the year-4 SV50 (r = 0.67). Multiple linear regression analysis found that available soil P (0–10 cm) and the P sorption class of the surface soil (0–2 cm), together with annual rainfall and a measure of the surface soil"s ability to retain moisture, could explain about two-thirds of the variance in the year-4 SV50 . The results from this Project indicate that there are a number of specific pasture environments in the higher rainfall regions of Australia where North Carolina reactive phosphate rock can be considered as an effective substitute P fertiliser for improved pasture.

scholarly journals A comparative analysis of the outcome of malaria case surveillance strategies in Sri Lanka in the prevention of re-establishment phase

2021 ◽  
Author(s):  
W. M. Kumudunayana T. de A. W Gunasekera ◽  
Risintha Premaratne ◽  
Deepika Fernando ◽  
Muzrif Munaz ◽  
M. G. Y. Piyasena ◽  
...  
Keyword(s):  
Sri Lanka ◽  
Case Reports ◽  
Individual Case ◽  
Case Detection ◽  
Malaria Surveillance ◽  
Blood Smears ◽  
Passive Case Detection ◽  
Routine Basis ◽  
Detection Strategies ◽  
Very High

Abstract Background Sri Lanka sustained its malaria-free status by implementing, among other interventions, three core case detection strategies namely Passive Case Detection (PCD), Reactive Case Detection (RACD) and Proactive Case Detection (PACD). The outcomes of these strategies were analysed in terms of their effectiveness in detecting malaria infections for the period from 2017-2019. Methods Comparisons were made between the surveillance methods and between years, based on data obtained from the national malaria database and individual case reports of malaria patients. The number of blood smears examined microscopically was used as the measure of the volume of tests conducted. The yield from each case detection method was calculated as the proportion of blood smears which were positive for malaria. Within RACD and PACD, the yield of sub categories of travel cohorts and spatial cohorts was ascertained for 2019. Results A total of 158 malaria cases were reported in 2017-2019. During this period between 666,325-725,149 blood smears were examined annually. PCD detected 95.6%, with a yield of 16.1 cases per 100,000 blood smears examined. RACD and PACD produced a yield of 11.2 and 0.3, respectively. The yield of screening the sub category of travel cohorts was very high for RACD and PACD being 806.5 and 44.9 malaria cases per 100,000 smears, respectively. Despite over half of the blood smears examined being obtained by screening spatial cohorts within RACD and PACD, the yield of both was zero over all three years. Conclusions The PCD arm of case surveillance is the most effective and, therefore, has to continue and be further strengthened as the mainstay of malaria surveillance. Focus on travel cohorts within RACD and PACD should be even greater. Screening of spatial cohorts, on a routine basis and solely because people are resident in previously malarious areas, may be wasteful, except in situations where the risk of local transmission is very high, or is imminent. These findings may apply more broadly to most countries in the post-elimination phase.

scholarly journals Spatial and Temporal Evolution of the Infiltration Characteristics of a Loess Landslide

2020 ◽  
Vol 9 (1) ◽  
pp. 26 ◽  
Author(s):  
Dongdong Yang ◽  
Haijun Qiu ◽  
Yanqian Pei ◽  
Sheng Hu ◽  
Shuyue Ma ◽  
...  
Keyword(s):  
Slope Stability ◽  
Slope Failure ◽  
Temporal Evolution ◽  
Infiltration Rate ◽  
Middle Part ◽  
Loess Landslide ◽  
Infiltration Rates ◽  
Disturbed Soil ◽  
Landslide Body ◽  
Over Time

Infiltration plays an important role in influencing slope stability. However, the influences of slope failure on infiltration and the evolution of infiltration over time and space remain unclear. We studied and compared the infiltration rates in undisturbed loess and disturbed loess in different years and at different sites on loess landslide bodies. The results showed that the average initial infiltration rate in a new landslide body (triggered on 11 October 2017) were dramatically higher than those in a previous landslide body (triggered on 17 September 2011) and that the infiltration rates of both landslide types were higher than the rate of undisturbed loess. The initial infiltration rate in the new landslide body sharply decreased over the 4–5 months following the landslide because of the appearance of physical crusts. Our observations indicated that the infiltration rate of the disturbed soil in a landslide evolved over time and that the infiltration rate gradually approached that of undisturbed loess. Furthermore, in the undisturbed loess, both the initial and quasi-steady infiltration rates were slightly higher in the loess than in the paleosol, and in the previous landslide body, the infiltration rate was highest in the upper part, intermediate in the middle part, and lowest in the lower part. This study can help us to better understand the evolution process of infiltration in undisturbed loess, previous landslides, and new landslides.

Corrigenda - A portable microcomputer-controlled drip infiltrometer. II. Field measurement of sorptivity, hydraulic conductivity and time to ponding

Soil Research ◽  
1985 ◽  
Vol 23 (3) ◽  
pp. 393
Author(s):  
BJ Bridge ◽  
PJ Ross
Keyword(s):  
Hydraulic Conductivity ◽  
Surface Soil ◽  
Sandy Loam ◽  
Application Rate ◽  
Variable Rate ◽  
Infiltration Rates ◽  
Constant Rate ◽  
Long Time ◽  
Loam Soil ◽  
Dry Soil

The lightweight portable drip infiltrometer described in Part I was used to determine the infiltration characteristics of a sandy loam soil. Sorptivity was determined by varying the application rate to maintain surface ponding and by measuring the time to ponding at a constant application rate. Saturated hydraulic conductivity was equated to the long-time steady-state application rate needed to maintain surface ponding. This rate could be determined to a precision of 0.5 �m s-1 (2 mm h-1) and agreed well with core data from 0.5 to 1.0 m depth in the profile. The results obtained were compared with ponded ring infiltrometer measurements. Sorptivities calculated from the ring infiltrometers were greater than those from the variable rate drip infiltrometer which in turn were greater than those from the constant rate drip infiltrometer. This was attributed to the effect of the macropores under the ponded rings and to confining the depth over which sorptivity was measured under constant application rate to the wetter surface soil. In dry soil, the drip infiltrometer measured low initial infiltration rates caused by poor wetting of the soil, but these were not measured by the ponded ring infiltrometers, which had a 50 mm head. In moist soil, poor wettability did not occur. Five equations for calculating sorptivity from measurements of time to ponding under a constant application rate of 8.3 �m s-1 (30 mm h-1) were used and four of these equations agreed within 20%. This was less than the range of sorptivities arising from uncertainties in determining the time to ponding, and the differences between the equations were attributed to the assumptions used in their derivation. It was concluded that any measurement of sorptivity on this soil was difficult to interpret because of non-uniformity in the upper soil profile.

scholarly journals DNA extraction technique for different rice varieties grown in Sri Lanka

2015 ◽  
Vol 3 (3) ◽  
pp. 398-401
Author(s):  
Ranganathan Kapilan
Keyword(s):  
Sri Lanka ◽  
Dna Extraction ◽  
Extraction Method ◽  
Extraction Methods ◽  
Rice Varieties ◽  
Modified Method ◽  
Dna Extraction Methods ◽  
Very High ◽  
Different Parts

Extraction of DNA is very important nowadays in bio-molecular researches. Extracted DNA should be purified and the quality of DNA should also be very high. The objective of the study was to develop a simple efficient method to isolate DNA from the rice varieties in an open laboratory environment, and to eliminate the usage of expensive chemicals and tools. The DNA extraction methods developed by the DNeasy plant kit method supplied by QIAGEN, Cheng et al., Doyle et al. and Michiels et al. were applied to five different rice varieties grown in different parts of Sri Lanka. Based on the quantity and quality of the extracted DNA tested by measuring the absorbance of DNA at 260 nm using Nanodrop® ND-1000 spectrophotometer and measuring the ratio of A260 / A280 and gel running on agarose, the efficiency of the extraction method chosen varied among rice varieties. Among the methods used, the methods introduced by DNeasy plant kit method supplied by QIAGEN and Cheng et al, yielded good and amplifiable quality DNA with satisfactory concentration for all the rice varieties tested. Therefore the modified method of Cheng et al, 1987 could be used to extract DNA from rice varieties instead of the commercially available expensive and hazardous DNeasy plant kit method supplied by QIAGEN.Int J Appl Sci Biotechnol, Vol 3(3): 398-401

scholarly journals A Sensitivity Analysis of Simulated Infiltration Rates to Uncertain Discretization in the Moisture Content Domain

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1192
Author(s):  
Lulu Liu ◽  
Han Yu
Keyword(s):  
Moisture Content ◽  
Nonlinear Dynamical System ◽  
Infiltration Rate ◽  
Hydrologic Model ◽  
Water Infiltration ◽  
Nonlinear Dynamical ◽  
Pore Sizes ◽  
Infiltration Rates ◽  
The Difference ◽  
Region Scale

An unconditionally mass conservative hydrologic model proposed by Talbot and Ogden provides an effective and fast technique for estimating region-scale water infiltration. It discretizes soil moisture content into a proper but uncertain number of hydraulically interacting bins such that each bin represents a collection of pore sizes. To simulate rainfall-infiltration, a two-step alternating process runs until completion; and these two steps are surface water infiltration into bins and redistribution of inter-bin flow. Therefore, a nonlinear dynamical system in time is generated based on different bin front depths. In this study, using rigorous mathematical analysis first reveals that more bins can produce larger infiltration fluxes, and the overall flux variation is nonlinear with respect to the number of bins. It significantly implies that a greater variety of pore sizes produces a larger infiltration rate. An asymptotic analysis shows a finite change in infiltration rates for an infinite number of bins, which maximizes the heterogeneity of pore sizes. A corollary proves that the difference in the predicted infiltration rates using this model can be quantitatively bounded under a specific depth ratio of the deepest to the shallowest bin fronts. The theoretical results are demonstrated using numerical experiments in coarse and fine textured soils. Further studies will extend the analysis to the general selection of a suitable number of bins.

scholarly journals Swine Finishing Room Air Infiltration: Part 1. Quantification and Prediction

2018 ◽  
Vol 34 (2) ◽  
pp. 413-424
Author(s):  
H T Jadhav ◽  
S J Hoff ◽  
J D Harmon ◽  
Igancio Alvarez ◽  
D S Andersen ◽  
...  
Keyword(s):  
Sea Level ◽  
Power Law ◽  
Pressure Difference ◽  
Construction Material ◽  
Weather Conditions ◽  
Infiltration Rate ◽  
Mechanically Ventilated ◽  
Infiltration Rates ◽  
Air Infiltration ◽  
Single Room

Abstract. Air infiltration through unplanned inlets is an integral component of any ventilation process. Air infiltration affects the quality of the room environment and can also increase winter heating costs. Precise data on air infiltration is very important in the design of animal room ventilation systems. Nineteen mechanically ventilated (negative pressure type) swine finishing rooms in Iowa were tested for their air infiltration potential. Using the data of 17 rooms, air infiltration rate through the whole room (i.e., total air infiltration, It), curtains (Ic), fans (If), and net building shell (other components, Io) were quantified. Power law equations were developed for infiltration prediction of different room configurations grouped on the basis of their construction style, age, ceiling material, curtain perimeter, and fan backdraft shutter area. All power law models reported in this study were adjusted to predict standard (sea level) infiltration rates. At 20 Pa pressure difference across the room envelope, the predicted standard It infiltration rate for the 17 rooms was 5.96±1.49 air changes per hour (ach); whereas, the predicted standard Ic, If, and Io infiltration rates were 1.49 ±1.00 ach (about 25% of It), 1.52 ±1.38 ach (about 26% of It) and 2.90 ±1.42 ach (about 49% of It), respectively. The standard It infiltration rate trended lower for rooms (n=8) from single room layout barns (5.85 ±1.66 at 20 Pa), rooms (n=8) having a non-metal ceiling (5.85 ±2.15 at 20 Pa), and rooms (n=8) aged = 13 years (5.85 ±2.15 at 20 Pa). The infiltration resistances, calculated using standard sea level infiltration rates, indicated that the curtain, fan, and other infiltration areas of swine finishing rooms changes with barn layout, age, construction material, and pressure difference. Methodology to convert measured infiltration rates to standard sea level weather conditions and to any desired room location was included. Keywords: Infiltration, Swine finishing Barns, Swine finishing rooms, Infiltration prediction, Infiltration quantification, Ventilation.

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