Lysimeter study to identify GPR response under different contaminant level in groundwater

Potentials of groundwater contamination due to different pollutant loads can be assessed using different technologies available through quality detection, mapping extend of the contaminant plume and migration of the plume. Real field situation is very complex and application of some techniques might be a challenging task especially with respect to data interpretation. Creating of controlled condition which represents the real field situation is very much important to understand the field situation and applicability of such techniques. Among the available geophysical methods, ground penetrating radar (GPR) technique is suitable for studying the subsurface features. A lysimeter (4.0 m x 1.0 m x 1.5 m (L x W x D)) study was conducted at the Meewathura farm of the Department of Agricultural Engineering, University of Peradeniya to verify the applicability of the GPR technique in detecting contamination level in groundwater. The lysimeter was filled with sand as a media and two iron bars (with a diameter of 5 cm) were placed at 1.0 m and 3.0 m length intervals at 0.2 m above from bottom of the lysimeter. GPR reflection surveys were carried out on lysimeter at different level of contamination. GPR wave response was studied under each situation and analyzed the reflected waves from bottom of the lysimeter and iron bars. 2D GPR wave simulations were carried out using GPRMAX2D for the same lysimeter conditions. For this purpose, a contamination plume with different EC values (to obtain different contaminant levels) in groundwater was introduced to the model domain. Both modeling result and lysimeter study were revealed that the energy of reflected wave attenuated and disappear the reflected event with increasing contaminant level (increasing EC)

Field mapping of wetting front using ground penetrating Radar under uniform and non-uniform wetting

This research was carried out to develop 2D and 3D maps of a wetting front and to identify potential preferential flow areas using Ground Penetrating Radar (GPR). GPR grid data were collected during uniform and non-uniform wetting experiments. Maps were prepared for different depth profiles for each data set, collected at different time intervals after starting water application. The wetting front had reached a maximum depth of 0.45–0.50 m within 25 hours of continuous wetting based on 2D and 3D GPR images. In the uniform wetting experiments, potential preferential flow zones could be identified in 2D and 3D maps

Drinking Water and Sanitation Conditions of Households in Tea Estates A Case Study from the Giragama Estate

Safe drinking water and adequate sanitation are considered as basic human rigths. The understanding ofhow many people do not have access to drinking water and sanitation may help to assess the communitieswho do not have access to the fundamentals needs and facing spread of communicable diseases. In SriLanka, the estate sector has comparatively low health and sanitation condition than the rural and urbansectors. The population coverage for water and sanitation services for urban, rural and estate sectors are100%, 82% and 62% and 100%, 82% and 55%, respectively in 2012. The Millanium Development Goals andNational Development Plan targets 80%, 90% and 100% of water for estate, rural and urban areas,respectively. In the case of sanitation they target 75%, 85% and 95% for estate, rural and urban areasrespectively. This study was conducted to investiage the drinking water and sanitation situation of househodsin two villages of the Giragama tea estate in the Central Province of Sri Lanka. The required data werecollected through a structured questioner from a randomly selected 26 households from Kudaoya and 35households from Kirimetiya watta of the Giragama estate. The main source of drinking water is unprotectedspring in Kirimettiya watta and piped water in Kudaoya. The percentage of improved source of drinkingwater is 77.2% and 94.9% in Kirimettiya watta and Kudaoya, respectively. A 51.4% and 34.6% of watercollection is done by females in Kirimettiya watta and Kudaoya, respectively. A 96.8% of households inKirimettiya watta have access to safer drinking water while it was 78.3% in Kudaoya. Boiling is found to bethe major means of treatment of drinking water for 85.3% of the population tested. Kirimettiya watta has87.3% improved sanitation facilities while it is 85.6% in Kudaoya. With respect to sanitation, 81.1% disposechildren’s faeces safely in Kirimettiya watta and this was 100% in Kudaoya. According to the overallanalysis, it can be concluded that the two villages considered in this study has a fairly good improveddrinking water facility and water availability. The households in Kudaoya have less awareness with regardto making drinking water safer. More than 85% of the households are using improved sanitation facilitiesand most of them have improved methods of childen’s fecal removal.KEYWORDS: Kirimettiya watta, Kudaoya, sanitation, drinking wate

Assessment of the Variability of Soil Properties for OFC Cultivation under Minor Irrigation Systems

Combined paddy and other field crops (OFC) fields are unique from other wetland or upland soils, because of seasonal alternation of wetting and drying conditions resulting anaerobic and aerobic conditions. Therefore, objective of this study was to assess spatio-temporal variation of soil properties in paddy fields under minor tanks with respect to OFC cultivation. Soil samples were collected at two soil depths from 24 locations covering the entire command area of the Bayawa Minor Irrigation Tank (MIT), Sri Lanka. Soil properties were analyzed and mapped using Arc GIS. Hardpan depth (HPD) was also determined by collecting undisturbed core samples at 0, 15, 25, 30, 45 and 60 cm depths from the same locations Statistical analysis was done to identify spatio-temporal variability of each property. Results revealed that, Bayawa command area showed low coefficient of variation (CV) for pH and bulk density, but high CV for saturated hydraulic conductivity (Ks). HPD was found to be varied in each section within the effective root zone. Overall, low Ks, high clay content, high field capacity, poor drainage and the presence of hardpan are major obstacles to introduce OFC. Therefore, introduction of site specific OFC by considering the variability of soil properties is very important for sustainability of the MIT system

Water Pollution in a Natural Stream and Its Impacts on Society and Environment: A Review of Studies on Meda Ela, Sri Lanka

Abstract: Meda Ela which originates from Kandy Lake and runs through Kandy city is considered to be one of most polluted tributaries of Mahaweli River. The objective of the study was to critically review the published research findings related to Meda Ela pollution to existing problems, research gaps and the means to rectify the situation. The review was carried out under the categories of socio-economic background, land use changes, sources of pollution, solid and waste water disposal, water quality, cost due to water pollution, economic benefits and major stakeholders and their interactions of Meda Ela. Study identified a very high urbanization rate in the watershed during the last decade compared to previous 30 years. Major point sources include the hospital, bus stand, railway station, central market and the residences on either side of Meda Ela. According to the literature, elevated pollution levels are reported during wet season and NO- 3, NH+ 4, PO3- 4, suspended solids, heavy metals, DO, BOD and COD showed above threshold limits. This is an indication of non-point source pollution which is responsive to hydrological conditions. Impacts of water pollution include vector borne diseases such as Dengu and Chickengunya, bad odour, flash floods and contamination of shallow groundwater with heavy metals. The social and management setup in the watershed is very complex since many stakeholders are involved in polluting and managing Meda Ela. The analysis revealed that the relationship among different stakeholders is highly diverse and as a result, their contribution to control water pollution in Meda Ela is also very different. Hence, a strong connection should be established between community and other stakeholders to develop an efficient and effective management plan to safeguard Meda Ela stream and its watershed

Improving water productivity in moisture-limited rice-based cropping systems through incorporation of maize and mungbean: A modelling approach

Crop and water productivities of rice-based cropping systems and cropping patterns in the irrigated lowlands of Sri Lanka have not been researched to the degree warranted given their significance as critical food sources. In order to reduce this knowledge gap, we simulated the water requirement for rice, maize, and mungbean under rice-based cropping systems in the Dry Zone of Sri Lanka. We evaluated the best combinations of crops for minimum water usage while reaching higher crop and water productivities. We also assessed the risk of cultivating mungbean as the third season/sandwich crop (i.e. rice-mungbean-rice) in different regions in Sri Lanka. In the simulation modelling exercise, APSIMOryza (rice), APSIM-maize and APSIM-mungbean modules were parameterised and validated for varieties grown widely in Sri Lanka. Moreover, crop productivities and supplementary irrigation requirement were tested under two management scenarios i.e. Scenario 1: irrigate when plant available water content in soil fell below 25% of maximum, and Scenario 2: irrigate at 7-day intervals (current farmer practice). The parameterised, calibrated and validated model estimated the irrigation water requirement (number of pairs of observations (n) = 14, R2 > 0.9, RMSE = 66 mm season−1 ha−1), and grain yield of maize (n = 37, R2 > 0.95, RMSE = 353 kg ha−1) and mungbean (n = 26, R2 > 0.98, RMSE = 75 kg ha−1) with a strong fit in comparison with observed data, across years, cultivating seasons, regions, management conditions and varieties. Simulated water requirement during the cropping season reduced in the order of rice (1180–1520 mm) > maize and mungbean intercrop = maize sole crop (637–672 mm) > mungbean sole crop (345 mm). The water productivity of the system (crop yield per unit water) could be increased by over 65% when maize or mungbean extent was increased. The most efficient crop combinations to maximise net return were diversification of the land extent as (i) 50% to rice and 50% to mungbean sole crops, or (ii) 25%, 25% and 50% to rice, maize and mungbean sole crops, respectively. Under situations where water availability is inadequate for rice, land extent could be cultivated to 50% maize and 50% mungbean as sole crops to ensure the maximum net return per unit irrigation water (115 Sri Lankan Rupees ha−1mm−1). Regions with high rainfall during the preceding rice cultivating season are expected to have minimum risk when incorporating a third season mungbean crop. Moisture loss through evapotranspiration from the third season mungbean crop was similar to that of a fallowed site with weeds.Authors acknowledge the funding received from the AusAIDCSIRO project “Improved climate forecasting to enhance food security in Indian Ocean Rim countries” (AusAID Agreement 59553) through the Agriculture Education Unit(AEU) ofthe Faculty of Agriculture, University of Peradeniya to conduct the study, and the Department of Agriculture, Sri Lanka for providing the access to collect secondary data on crop performances and management, and weathe