How to Use the Images
Illustrations 1a and 1b
Photo 3: Out-take Connecting the Leasburg Canal with the Doņa Ana Lateral, 1908
(National Archives and Records Administration; Walter J. Lubken, photographer.)
Questions for Photo 3
1. Examine the photo, which shows water being diverted from the Leasburg Canal on the left into the Doña Ana Lateral on the right through a connecting channel called an "out-take." Find the tall poles set in horizontal circular wheels. These control gates open to allow water to flow from the canal to the lateral. Note the concrete structure in the Leasburg Canal that looks something like a bridge; it's called a "check structure." Compare the surface elevation of the water in the canal above the check structure with the lateral's water surface elevation. Why is the water level in the canal higher than the level in the lateral? Explain your answer. How do you think the check contributes to maintaining the correct elevational relationship between the two?
2. Notice the high earthen embankments along the outside edges of both the canal and the lateral. Does it look like the countryside is higher or lower than the top of the water in the canal and lateral? Is it higher or lower than the top of the embankments? What purpose do you think the embankments serve?
3. Notice that neither the canal nor the lateral appears to have a lining. Canals could be "earthen" (unlined), or lined with various materials such as rock, concrete, etc. What purpose do you think lining would serve? Why would it only be used sometimes? Do you think cost might affect the decision to line a canal or not? Examine the out-take and the check. What material appears to have been used to construct these features and why do you think it was used there and nowhere else? Reclamation eventually lined most of its canals with concrete and replaced wooden structures with concrete ones. Why do you think they did that?
Click for a larger version of Photo 3.