Journal of Irrigation and Drainage Engineering

The problems of getting irrigation water to lands to be irrigated in the right amount, at the right place and at the right time are discussed. A brief review of the methods of irrigation water delivery is presented along with a more detailed discussion of rotation delivery. A step by step detailed procedure is shown for setting up a rotation delivery schedule. The resulting schedule provides for equity between users with respect to volume of water per unit area and time of irrigation turn (daytime or night).

Injection of air into the vadose zone has made water available for recovery by conventional means at two test sites on the High Plains of Texas. The cost of this water, exclusive of research costs, is estimated to be about $50 per acre‐ft. Large quantities of water may be available for recovery in aquifers which have experienced long term water level declines, and where a layer of low permeability material is available to prevent rapid escape of the injected air. A possible explanation of the mechanism of removal is examined, and the conclusion reached that movement occurs because of unbalanced pressure forces on the capillary water. These forces are caused by the flow of the injected air past the pore water.

The experiment was conducted in lysimeters for studying the evaporation from soil surface in relation to water table depth and standard pan evaporation. Dummy variables 1 and 0 were used as an alternative to analyze the variance and covariance to compare the soil surface evaporation difference between water table depths. The dummy variable regression analysis can simultaneously test the difference between two regression lines whether due to slope coefficients or intercept terms. The water table depth was significantly affected on the soil surface evaporation. The soil surface evaporation for 38 cm water table was significantly smaller value than that for the 8 cm water table. The soil surface evaporation in wet season had a smaller deviation from the standard pan evaporation and had a more homogeneous distribution within the wet season than that in the dry season.

A kinematic‐wave model of furrow irrigation under both continuous and surged flow management was developed and verified. Numerical solution of the differential continuity equation is accomplished with a Eulerian first‐order integration coupled with the assumption that flow rate and flow area are uniquely related by the Manning uniform flow equation. Field data from three Colorado sites, a Utah site, and an Idaho site were used to verify the model's continuous flow simulation of advance and recession. The sites represented a wide range of soil types, field slopes and lengths, and duration of the irrigation event. Companion data from the Utah and Idaho sites were used to verify the model's analysis of surge flow conditions.

Laboratory tests were conducted to determine the effects of total opening area, location of openings and gravel envelope on radial flow to 100 mm (4 in.) diam corrugated plastic drains. Radial flow theory was used to evaluate the effective drain tube radius, $r_e\text{,}$ and the drainage transfer coefficient for the corrugated tubes. The effective radius increased with total perforation area as expected, but the location of the drain tube perforation had little effect on $r_e\text{.}$ The greatest increase of effective radius for an increase in perforation area occurred between areas of $38-75{\mathrm{cm}}^2/m$ where $r_e$ increased from 5 mm to about 21 mm. Use of a 50 mm thick gravel envelope resulted in an increase in the effective drain radius for a 100 mm diam pipe from 5–36 mm. Experimental results for the effective radius were compared to theoretical values obtained from an earlier solution for circumferential openings. The experimental results were in close agreement with predicted values for a 1.0 mm opening width.

A simulation model for assessing the water demands of large irrigation areas is developed and applied to the mid‐Canterbury region of New Zealand. Observations from historical water use patterns provide a basis for demand modeling using simplified irrigation watering strategies, highlighting climatic time variability as the single most important influencing factor. Per unit area irrigation demands are first estimated for each identified unique combination of soil, crop type and irrigation strategy using daily soil moisture balance simulation over a number of seasons of recorded climate data. These are then combined using crop areas and efficiency weights to give time patterns of areallyaggregated water demand. The model is checked against field trial data, calibrated against water use in an existing irrigation scheme, and applied to demand estimation for a large proposed future project.

Soil erosion is a serious problem in India. In the absence of precise estimates of total erosion in the country, this paper presents a method to arrive at a first estimate of soil erosion, sediment loads of rivers and sedimentation in reservoirs. In this analysis, existing annual soil loss data for 20 different land resource regions of the country sediment loads of some rivers, and rainfall erosivity for 36 river basins and 17 catchments of major reservoirs are utilized and statistical regression equations are developed for predicting sediment yield. Using these expressions and corresponding values of area, rainfall, rainfall erosivity and surface runoff, annual values of total sediment loads of streams, sediment deposition in reservoirs, and sediment lost permanently into the sea are estimated. According to this estimate, which is treated as a first approximation, soil erosion is taking place at the rate of 16.35 ton/ha/annum which is more than the permissible value of 4.5–11.2 ton/ha. About 29% of the total eroded soil is lost permanently to the sea. Ten percent of it is deposited in reservoirs. The remaining 61% is dislocated from one place to the other.

A previously reported photographic recording device has been modified to accommodate available equipment and conditions. A battery operated system for tripping the shutter of an automatic advance camera, instead of a mechanical linkage, was developed to obtain daily data from a remotely located anemometer. The system includes a rotating drum recorder with an 8-day clock, a 24-volt DC battery power pack, solenoid plunger, capacitor, and microswitch. Cautionary procedures are described for effective operation of the system. A periscope with magnifying lenses was used to locate the camera enclosure and operating mechanism below the plane of the anemometer cups to minimize their effect on the air flow near the instrument. Specific length dimensions of the periscope to provide clear, readable images of the film negative are presented.