Field evaluation of passive capillary samplers for estimating groundwater recharge

Passive capillary samplers (PCAPS), which sample water from the vadose zone via a hanging water column in a fiberglass wick, have shown potential to provide superior estimates of soil water flux compared to alternative methods. The objectives of this study were to evaluate the performance of PCAPS under natural rain-fed conditions concerning (1) their operational characteristics and (2) their ability to estimate soil water flux. Forty-two PCAPS were installed in 21 commercial agricultural fields in Lane County, Oregon. Monthly measurements of soil water flux and precipitation were recorded at each site for the 4-year project duration. Of the 42 installed PCAPS, 12 samplers at six sites were inoperable or did not operate efficiently: 10 samplers were consistently below the water table, which overflowed the collection vessels rendering the samplers inoperable. Only two of the PCAPS exhibited technical failure resulting in unusually low collection efficiencies, thought to be due to a collapse of the collection vessel from oversuction during sample retrieval. On average, the 30 remaining PCAPS measured soil water flux 25% greater than that obtained from a water balance estimate. This discrepancy represents ∼8% of the total annual precipitation and irrigation each site received. PCAPS collection efficiency was found to be significantly correlated (R2 = 0.75) to the water balance yearly estimated recharge. The difference between PCAPS measured and water balance estimated percolation could be the result of inaccuracy in water balance evapotranspiration estimates and/or oversampling in the presence of high water tables. To estimate the mean yearly recharge at each site with a 30% bound on the mean at the 0.05 confidence level, eight PCAPS are required. This number corresponds closely to the results of Brandi-Dohrn et al. [1996a] and is thought to be due to intrinsic variability of percolation

USCID fourth international conference

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.A large percentage of pasture in the Upper Klamath Basin is irrigated by "wild flood" surface irrigation methods. Efforts underway to improve irrigation efficiency in the basin using federal funds have included conversions to sprinkler irrigation systems and to higher efficiency graded border surface irrigation systems. With dramatic increases in power rates for agricultural users on the horizon, surface irrigation enhancements have significant promise to increase water use efficiency without substantially increasing production costs. While these projects generally do not solve the basin's water supply problems, they do provide a significant enhancement to surface water quality by reducing sediment and nutrient containing surface return flows. In areas where groundwater levels are declining due to irrigation pumping, these projects can also reduce stresses on groundwater supplies. A project implemented near Sprague River is used as a case study to describe how the simple conversion from ditched to piped laterals, creation of new border ridges, and improvements to irrigation scheduling can dramatically increase irrigation application efficiency while at the same time reducing pumping costs and groundwater withdrawals without any increase to daily labor requirements

Low-cost, local production of a safe and effective disinfectant for resource-constrained communities.

Improved hygiene depends on the accessibility and availability of effective disinfectant solutions. These disinfectant solutions are unavailable to many communities worldwide due to resource limitations, among other constraints. Safe and effective chlorine-based disinfectants can be produced via simple electrolysis of salt water, providing a low-cost and reliable option for on-site, local production of disinfectant solutions to improve sanitation and hygiene. This study reports on a system (herein called Electro-Clean) that can produce concentrated solutions of hypochlorous acid (HOCl) using readily available, low-cost materials. With just table salt, water, graphite welding rods, and a DC power supply, the Electro-Clean system can safely produce HOCl solutions (~1.5 liters) of up to 0.1% free chlorine (i.e.,1000 ppm) in less than two hours at low potential (5 V DC) and modest current (~5 A). Rigorous testing of free chlorine production and durability of the Electro-Clean system components, described here, has been verified to work in multiple locations around the world, including microbiological tests conducted in India and Mexico to confirm the biocidal efficacy of the Electro-Clean solution as a surface disinfectant. Cost estimates are provided for making HOCl locally with this method in the USA, India, and Mexico. Findings indicate that Electro-Clean is an affordable alternative to off-the-shelf commercial chlorinator systems in terms of first costs (or capital costs), and cost-competitive relative to the unit cost of the disinfectant produced. By minimizing dependence on supply chains and allowing for local production, the Electro-Clean system has the potential to improve public health by addressing the need for disinfectant solutions in resource-constrained communities

Alternativa para caracterização da condutividade hidráulica saturada do solo utilizando probabilidade de ocorrência Alternative of characterization to the soil hydraulic conductivity utilizing probability of occurrence

A Condutividade Hidráulica Saturada (Ksat) devido à sua importância em informar sobre a capacidade de transporte de água, solutos e substâncias químicas no solo deve ser bem caracterizada, pois de um modo geral, seu valor é utilizado nos cálculos de fluxos no solo. Com o objetivo de propor uma alternativa para caracterizá-la, a partir de uma série de dados, utilizou-se a função densidade de probabilidade lognormal para obter os valores da propriedade correspondentes aos níveis de 5 a 95% de probabilidade de ocorrência, visando descrever e indicar melhores valores a serem adotados como Ksat para a área considerada. Como resultado obteve-se uma análise da variável em termos de probabilidade de ocorrência. Essa representação, na medida em que associa o nível de probabilidade ao valor adotado para a propriedade, permite ao pesquisador avaliar o risco na estimativa de medidas dependentes de Ksat, visto que esta propriedade no solo apresenta alta variabilidade.<br>The Saturated Hydraulic Conductivity of the soil (Ksat) due to its importance in inform about the capacity of transport of water, solutes and chemical substances in the soil should be well characterized, since in general, this value is used in calculations of flows in the soil. Aiming at proposing an alternative to characterize the Ksat, starting from a series of data, the function density of probability lognormal was used to obtain the values of the property which corresponde to the levels of occurrence probability from 5 to 95%, in order to describe and to indicate better values to be adopted as Ksat for the considered area. As a result, it was obtained an analysis of the values of the variable in terms of occurrence probability. This representation, associating each value to a probability level, allows to the researcher to evaluate the error on estimation of measurements that depend on Ksat, due to the fact that, this property in the soil presents high variability