Irrigation ditches

Figure 2—Sugar cane about 6 weeks old which has had one spray of 2,4-D amine and 2 sprays of 6CA-4. Weed control is excellent both in irrigation ditches and within rows...

The water fern (Salvinia auriculata Aublet) may cover irrigation ditches and obstruct machinery and has assumed pest proportions in Ceylon (48). A similar species (S. rotundifolia Willd.) has formed solid blankets over irrigation ditches and ponds in Puerto Rico. It is important in the breeding of the malaria vector in... 

Aquatic seeds in irrigation ditches interfere with the flow of water and often result in serious loss to farmers. Chlorinated benzene with appropriate emulsion stabilizers has proved effective in the control of such weeds. The Bureau of Reclamation through its Denver laboratories tested methyl substituted benzenes and found them equally toxic to aquatic weeds. As a result, the aromatic solvents, both from coal and petroleum sources, are proving a boon to farmers. 

The most common type of pump used is the sump pump shown in Fig. 25.8. The vast majority of the pumps in the world are of this type. They are the sort of pumps used to pump water out of shallow wells and from irrigation ditches. In New Orleans, we use thousands of these pumps to push rainwater over the levees and into the mighty Mississippi River. 

Smith, A.E., R. Grover, G.S. Emmond, and H.C. Korven (1975). Persistence and movement of atrazine, bromacil, monuron, and simazine in intermittently-filled irrigation ditches. Can. J. Plant Sci., 55 809-816. 

Equipment to measure, proportionally divert, and collect the surface runoff was installed at the end of the irrigation ditch-draining test plot. The measuring apparatus consisted of an up-channel and apron, Parshall flume, stilling well, and water level recorder. A flow-splitting device was attached to the downstream side of the flume. One third of the flow was diverted to a settling tank where it was sampled. A 3-hour retention time was allowed for the water-borne silt to settle. A proportional part of the settleable silt was collected for analysis. 

Do not allow runoff or spray to contaminate wells, irrigation ditches, or any body of water used for irrigation or domestic purposes. 

This product is water-soluble and can move with surface runoff water. Do not contaminate cropland, water, or irrigation ditches. 

A fluid flow is classified as being internal or external, depending on whether the fluid i.s forced to flow in a confined channel or over a surface. The flow of an unbounded fluid over a surface such as a plate, a wire, or a pipe is external flow. The flow in a pipe or duct is internal flow if the fluid is completely bounded by solid surfaces. Water flow in a pipe, for example, is internal flow, and airflow over a ball or over an exposed pipe during a windy day is external flow (Fig. 6-8). The flow of liquids in a duct is called open-channel flow if tlie duct is only partially filled with the liquid and there is a free surface. The flows of water in rivers and irrigation ditches are examples of such flows. 

Moist open ground, banks, low woods, along streams and irrigation ditches, especially in alkaline clay soil, Louisiana and Texas, throughout Mexico, up to 2,000 meters altitude also in western Cuba. 

In Example 6,13 the wetted perimeter was the entire perimeter of the duct. Here we do not include the perimeter facing the air, because the air exerts little resistance to the flow, compared with the walls of the canal. You can verify this by watching the flow of leaves or bits of wood on any open stream or irrigation ditch those at the center move much faster than those at the edges. If the air restrained the flow as much as the solid walls, then the whole top surface of the flow would not move at all, just as the fluid right at the solid boundaries does not move. Therefore, the hydraulic radius is... 

The absolute roughness of a concrete-lined irrigation ditch is estimated from Table 6.2 to be 0.01 ft, so the relative roughness is... 

Mead, E. (1908). An Australian irrigation-ditch water meter. Engineering News 59(Mar.26) 346. Mead, E. (1930). The Colorado River. Engineering News-Record 104(6) 240-246. P... 

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