FIGURE 15.-Transport and placement of transmission line towers by helicopter, especially suitable for construction in remote areas, may become commonplace in the future. HYDRAULICS (INCLUDING OXYGEN CONTENT OF WATER) Flow-measurement equipment Many devices and structures have been developed for measuring the flow in domestic, industrial, and irrigation supply systems. Nearly all of these are designed to operate in conjunction with separate equipment used to control flows. A few serve the dual purpose of both control and measurement. Flow recorders needed Open-channel irrigation systems frequently use measuring devices calibrated in terms of water-level differences. As these differences vary, the discharges change. Instantaneous flow rates can be determined by measuring water levels upstream and downstream of the device. To integrate total flow, however, involves continuous measuring by recording facilities. Considerable numbers of inexpensive accurate recorders could be utilized in the management of water deliveries. New water measurement devices for both open channel and closed conduit flows are desirable. Of the many devices now available, few offer the accuracy required under variable operating conditions. Standardizing equipment would effect economies in initial installation, but more particularly in maintenance. Testing and calibration of weirs and studies needed Compound weirs, a combination of V-notch and rectangular weirs, for accurately measuring small as well as large flows, have been investigated and calibrated. Adjustable rectangular and Cipolletti weirs have been tested to determine the accuracy for various normal settings and flow approach conditions. The velocity of the flow toward a weir and the velocity distribution in this flow will influence the measuring accuracy of the weir. More attention should be given to evaluating these influences. Propeller meters, critical depth meters, meter gates, displacement meters, radial gates, slide gates, and valve studies Many commercial devices have been considered and some of these have been tested to delineate their capacities and limitations and to determine the influence of physical characteristics and flow conditions on their accuracy. Propeller meters, critical depth meters, meter gates, displacement meters, radial gates, slide gates, and valves have been studied and their suitability and accuracy as measuring devices evaluated. Radioisotopes in water measurement A recent innovation in the field of water measurement is the partial development of radioisotopes methods for discharge measurements and calibration of devices in operating systems. Extensive information is not yet available on the capabilities of these methods for general measurement use, but the potential advantages would seem to justify continued research. Equipment to inject isotopes into flowing water and electronic instruments for detecting passage in a flow system are needed. Techniques for integrating the intelligence from recording instruments require development. Radioisotopes in detecting seepage and permeability in soils. Radioisotopes are also being used to detect seepage in canals and to measure permeability of soils. Dilution of tracers provides a measure of flow velocity and direction of seepage. Advanced equip ment and techniques are needed to derive maximum benefit of these methods of measurement. Turnouts for closed conduit irrigation systems Much has been accomplished in recent years toward the improvement and simplification of turnouts for closed conduit irrigation distribution systems under moderate and high heads. Baffled out lets at the end of conduits and sudden enlargements in conduits downstream from control gates have been developed. Both types of design have been used successfully in the field, the baffled outlet with heads up to about 150 feet and the sudden enlargement with heads of about 400 feet. The structures are compact and economical to build Such turnouts serve to eliminate cavitation damage, vibration, and related noise. Chart establishing rock size for controlling erosion Where turnouts are built in easily erodible material, and exit velocities are sufficient to cause erosion, the channel banks must be protected to prevent undermining of the structures. Riprap frequently used for this purpose. Using available data from labora tory tests and field observations, a chart was developed for deter mining rock size required for velocities up to 20 feet per second. This chart has simplified the riprap design problem. Steel jacks and jetties When streams flow through wide flat valleys there may be consider able meandering and severe erosion of the banks. Large quantities of water may be lost by seepage and evaporation. Steel jacks and jetties have been used in recent years to stabilize river channels and thus save much water as well as prevent undue damage to the banks and adjoining farmland. Laboratory and field investigations in recent years have been used to develop design procedures for jack and jetty systems to stabilize river channels. Dissipating energy in flowing water Protection of the downstream foundations of hydraulic structures used to store and control water resources is a frequent consideration in design of Bureau projects. Facilities have been developed for dissipating the energy in flowing water in outlet works and spillways so that releases can be made without damaging the structures or their foundations. Developments have included hydraulic jump basins. vertical stilling wells, impact basins, flip buckets, and special basins for particular gate and valve designs. Of particular note are the stilling basin developed for the Bureau's hollow-jet valve, the vertical wells with sleeve valves to release and regulate flow into canals, and the flip bucket for tunnel spillways. Dissolved oxygen content in water Research is being conducted to investigate the effect of engineering structures for the impoundment and regulation of waters for irriga tion, power, and flood control, upon the dissolved oxygen content of FIGURE 16.-A movable-bed hydraulic model was constructed in the laboratories to develop design procedures for the most economical arrangement of steel jacks and jetty fields to control and stabilize meandering, sediment-laden rivers, to protect banks from erosion by floodwaters, and to reduce water losses from evaporation and transpiration. Fine light-colored sand represents the riverbed load while black graunulated plastic represents the suspended load. reservoirs and streams in Western United States. The dissolved oxygen content of water is vital to life processes. Dissolved oxygen sustains aquatic life, consumes natural, human, and industrial wastes in the water, and contributes significantly to taste. The content varies greatly with temperature and atmospheric pressure. Concentration in parts per million is surprisingly low, seldom exceeding 10 parts per million. The broad investigative program has the ultimate goal of using the increased knowledge to attain more favorable dissolved oxygen content in reservoir and river systems. Dissolved oxygen increased by turbulence Such factors as vegetal land management, hydrologic characteristics of watershed, population density, industrial development, and engineering structures must all be considered in determining and preserving the optimum dissolved oxygen regime. The formation of reservoirs behind dams has necessarily caused inundation of streamflow channels, thereby reducing the opportunity of natural replenishment of oxygen by turbulence. Moreover, the vegetation of the reservoir soil has a definite oxygen demand of its own which tends to deplete the available oxygen supply. Finally density stratification of the water in some reservoirs has been observed; this condition also has an adverse effect on the dissolved oxygen content, particularly in those reservoirs where no seasonal overturn is experienced. Industrial waste in streams In addition to attrition in impounded waters, the demands of an increasing population and the greatly intensified usage of both stored and flowing water have placed a heavier load of human and industrial wastes upon streams already somewhat depleted of dissolved oxygen. This condition is intensified in reservoirs having a long carryover storage period. Bacterial action Since the dissolved oxygen content of water may change rapidly due to bacterial action or to the presence of impurities, it has been essential that testing be performed almost immediately after collection of the samples. This necessitates the availability of testing equipment at each sampling site. Although this requirement can be met for sampling sites within easy access of an analytical laboratory, such is not the case for more remote areas. Collection of samples has been accomplished with a new device developed by the Bureau for the collection of water samples in streams and reservoirs at a specified depth. The samples are collected in standard dissolved oxygen bottles in which the dissolved oxygen can be chemically "fixed" for determination of content. Artificial oxygenating equipment needed As water resources are impounded in new reservoirs, and the reuse of water increases, studies of oxygen depletion assume greater importance. The turbulence in streams formerly provided the mechanism to maintain adequate dissolved oxygen in streams. Thus, fish and wildlife were sustained, and micro-organisms which attack organic pollutants could multiply. As the lengths of open turbulent waters decrease, the need for artificial oxygenating equipment increases. Epoxies PLASTICS Epoxy adhesives are used for bonding rubber sealing strips on the leaves of butterfly valves. Epoxy resins are being used for bonding fresh portland cement concrete to hardened concrete, for bonding hardened concrete to hardened concrete, and as the binder in epoxy mortars and concretes. The materials and techniques are particularly useful in concrete repair. A one half-inch epoxy bonded floor can be used in lieu of the conventional 3- or 4-inch finish floor at lower cost and at considerable weight savings. Bureau laboratory-designed epoxy resin mortars have proven to be stronger, more abrasion resistant, and more durable than commercially available epoxy mortars. Polysulfide synthetic rubber and rubberized asphalt Polysulfide synthetic rubber materials are specified for sealing construction joints in dams and powerplants. A rubberized asphalt is used for sealing joints in concrete canal linings. Plastics and their uses Plastics are being used for canal linings, cutoff walls, and small reservoir linings; in flap-valve weep drains; and in curing films and polypropylene tubing for piezometer installations. |