Irrigation Water Salt Concentration Influences on Sediment Removal by Ponds

Irrigation water salt concentration effects on sediment pond efficiency were investigated to demonstrate the necessity of considering the salt concentration in the irrigation waters when designing sediment retention ponds. The influence of dissolved salt was determined by adding concentrated CaCl2 solutions to three ponds and then measuring electrical conductivities and sediment concentrations at the pond outlets. Increasing the salt concentration increased the sediment removal efficiencies when the retention time in the pond exceeded 1 hour or the inflow sediment concentration exceeded 500 ppm for the three soils studied. Adding salt to laboratory soil sample suspensions increased the settling rates for the two soils studied. That data indicate that the salt concentration in irrigation water is an important factor in determining sediment pond size and retention time. Using pond design criteria obtained from sediment ponds receiving water of a given salt concentration to design ponds that will receive water with a different salt concentration should include adjustments for salt concentration differences. A simple laboratory test is suggested to predict which soils will respond to irrigation water salt concentration changes that are likely to result in sediment pond efficiency changes

Field Evaluation of Seepage Measurement Methods

Irrigation project design, operation and maintenance, and canal-lining research and development require accurate and economical measurements of seepage rates. Drastically new methods for measuring seepage have not been developed, so existing field methods must be used. Each of these methods warrants an evaluation of its capabilities and limitations. This paper relates experiences with ponding tests, seepage meters, and inflow-outflow methods of measuring seepage from canals. The results reported here represent the combined efforts of the University of Idaho Engineering Experiment Station, the Agricultural Research Service, and the U.S. Bureau of Reclamation. The study was performed in 1965 and 1966 on a 4.5-mile reach of the A and B Irrigation District Main Canal near Paul, Idaho. This canal is a part of the Minidoka Project of the U.S. Bureau of Reclamation. It is 25 to 30 feet wide with a gradient of about 0.5 feet per mile and flows at a depth of 5 to 5.5 feet during the irrigation season. Soils throughout the test reach are very uniform and consist almost entirely of Portneuf silt loam. A compacted, slightly cemented silt layer from 12 to 24 inches thick intersects the canal cross section throughout most of the the test reach. The flow system beneath the entire test reach is under tension gradients due to an impeding layer near the soil surface of the canal cross section. Devices for recording water measurement were installed by the Bureau of Reclamation at the inlet and outlet and at all turnouts on the reach. A water budget for the irrigation season was maintained on this reach for 3 years, and the loss rates for 2-week periods were computed

Frequency Analysis of Snow Course Data

The revised log-Pearson Type III frequency analysis was applied to data from 13 snow courses in five western states having a data base of 26 to 49 years. January through May monthly data for depth, water content and snow density were analyzed. The procedure provides good estimates of mid- and high-range depth and density values while overestimating near zero values on some courses. Generally for the 13 courses the over-estimation occurred whenever water content values were less than 2 to 3 inches. This is the minimum depth often considered for snowmobiling and skiing activities. Other frequency techniques should be considered for courses where estimates of values less than 2 inches are required such as for runoff predictions

Controlling erosion and sediment loss from furrow-irrigated cropland

Irrigation-induced erosion and subsequent sediment loss is a serious agricultural and environmental problem. Recent recognition of this problem has stimulated the development and evaluation of erosion and sediment-loss-control technology. Research results indicate that the application of the technology available today can reduce sediment loss by 70-100%. Important practices include irrigation-water management, sediment-retention basins, buried-pipe tailwater-control systems, vegetative filter strips, tailwater-recovery systems, keeping crop residues on the soil surface and in furrows, and implementing conservation tillage practices

Some Aspects of Sedimentation Pond Design

Erosion and sedimentation are normal geologic processes which are usually accelerated by irrigating agricultural lands. Of the sediment in irrigation runoff, 70% was removed in a sedimentation pond. Removal efficiency correlated well with flow rate and sediment concentration. Pond design should provide maximum velocity reduction early in ponding, allow adequate storage space for the larger particles, and decrease the flow depth toward the outlet while maintaining a constant forward velocity. This requires a fan-shaped pond, deeper at the inlet and decreasing in depth while increasing in width toward the outlet. This pond shape fits well into natural swales or draws

Management practices for erosion and sediment control in irrigated agriculture

Irrigation erosion and subsequent sediment losses to rivers and streams continue to be serious problems confronting irrigated agriculture. The seriousness of these problems depends upon user concerns which in turn depend upon geographic area and populations. Erosion problems are less severe in California than in Idaho, but the concern for controlling water quality can be greater in parts of California because of subsequent water uses. Basin irrigating rice can reduce suspended sediment loads in water because the basins serve as sediment retention basins. Furrow erosion causes significant suspended sediment loads in return flows in California, but the problem is much more severe in Idaho. Topsoil redistribution by furrow erosion and sedimentation has reduced potential crop yields by approximately 25%. Several sediment loss control practices have been developed and evaluated, and are effective, but costs deter their application. Research is presently directed toward controlling erosion along irrigation furrows. Methods to increase soil cohesion and utilize residues in minimum tillage and no-till systems have high potential for controlling erosion and sediment loss during the next decade

Predicting Irrigation Return Flow Rates

DESIGNING efficient sediment ponds requires data on expected sediment concentration and particle size distribution and on stream flow rate and volume. With these data, ponds may be designed to trap given particle sizes, and the quantities of trapped and passed sediment can be computed (Bondurant et al., 1975). In the context of Public Law 92-500, the Clean Water Act amendments of 1972, return flow from man-controlled irrigation may be classified as point source pollution and, therefore, permits may be required to discharge these return flows into rivers or streams. Little is known about return flows from most irrigation districts. Water, sediment, and chemical balances of the Twin Falls Canal Company and the Northside Canal Company areas in southern Idaho yielded information on flow and sediment concentrations and volume (Brown et al., 1974). Many of the return flow streams in this area had not been previously studied, and very little was known about their flow characteristics. Many return streams are ephemeral, flowing only in response to runoff from irrigation and regulation waste. More information is needed on these streams so that efficient and economical sediment ponds may be designed and constructed. If a pond is designed for too small a stream, the efficiency will be low and sediment removal will not be adequate. If the pond is designed for too large a stream, the efficiency will be improved but the cost will be greater than necessary. Hydrologic techniques for predicting, stream flow rates are mainly concerned with peak flows and maximum and minimum expected annual runoff. Predictive techniques utilize double-mass plots, rating curves, and extreme value techniques (Linsley et al., 1949). These techniques are for precipitation induced runoff and not for irrigation runoff. New techniques for predicting return flow rates from irrigated areas need to be developed

Ponding Surface Drainage Water for Sediment and Phosphorus Removal

SEDIMENT and phosphorus (P) removal efficencies of a sediment-retention pond with a capacity of about 3400 m³ receiving surface water runoff from 4050 ha of irrigated land, were measured for five years. Average daily flow through the pond, during the irrigation runoff period, was 347 L/s, with a pond retention time of 2.7 h. The pond removed 65 to 76 percent of the sediment, and 25 to 33 percent of the total P entering the pond. Sediment and phosphorus removal efficiencies depended upon the flow rate and the sediment concentration of surface return flow entering the pond. Sediment and phosphorus were most efficiently removed when the stream flow was 340 to 453 L/s and the sediment concentration was in the range of 20 to 750 mg/L. Sediment removed from the pond was used to cover protruding basalt to improve and expand a golf course

Plastic Casings for Soil Cores

Soil core samples with substantially undisturbed structure are often taken for laboratory evaluation of physical properties, particularly hydraulic conductivity. Most samplers for obtaining undisturbed samples use either a solid metal liner or a split metal liner to hold the sample. Cores taken in solid liners are trimmed, capped and left in the liner for transportation and testing. Samples taken in split liners are usually removed from the liner, trimmed and cased by painting with paraffin or plastic cement. Undisturbed soil cores require gentle handling to prevent breakage during sampling, trimming, packing, shipping and conducting laboratory tests. Core samples in solid liners can develop flow paths between the liner and the core, especially when making hydraulic conductivity measurements. Such flow paths may develop without being detected and will result in erroneous conductivity values. Samples that have been cased with paraffin or fluid plastic are not as subject to developing flow paths between the core and the easing, but the casing material fills some of the pore space, thus creating an indeterminate cross-sectional area

A Decommissioned LHC Model Magnet as an Axion Telescope

The 8.4 Tesla, 10 m long transverse magnetic field of a twin aperture LHC bending magnet can be utilized as a macroscopic coherent solar axion-to-photon converter. Numerical calculations show that the integrated time of alignment with the Sun would be 33 days per year with the magnet on a tracking table capable of $\pm 5^o$ in the vertical direction and $\pm 40^o$ in the horizontal direction. The existing lower bound on the axion-to-photon coupling constant can be improved by a factor between 50 and 100 in 3 years, i.e., $g_{a\gamma\gamma} \lesssim 9\cdot 10^{-11} GeV^{-1}$ for axion masses $\lesssim$ 1 eV. This value falls within the existing open axion mass window. The same set-up can simultaneously search for low- and high-energy celestial axions, or axion-like particles, scanning the sky as the Earth rotates and orbits the Sun.Comment: Final version, accepted for publication in Nucl. Instr. Meth. A. More information can be found at http://wwwinfo.cern.ch/~collar/SATAN/alvaro.htm