How to Use the Images
Illustration 1a: The Mesilla Valley Just Below the Leasburg Diversion Dam Today: northern portion
(Elephant Butte Irrigation District [Doņa Ana County, New Mexico] National Register Nomination)
Illustration 1b: The Mesilla Valley Just Below the Leasburg Diversion Dam Today: southern portion
(Elephant Butte Irrigation District [Doña Ana County, New Mexico] National Register Nomination)
The U.S. Geological Survey map from which this detail was taken is part of the National Register nomination for the Elephant Butte Irrigation District. The two sections overlap somewhat and the northern section is wider than the southern one. They can be combined by aligning them on the Rio Grande and the Leasburg Canal.
Questions for Illustrations 1a and 1b
1. Find the Leasburg Diversion Dam at the top of the illustration. This section of the canal map shows the oldest part of the Rio Grande Project. How long did it take to complete this part of the Project (refer to Reading 3, if necessary)? The illustration shows the Mesilla Valley between the Leasburg Diversion Dam and the town of Leasburg, which is about 12 miles north of Las Cruces. Find this area on Map 2. How much of the whole Rio Grande Project does this illustration represent?
2. This illustration is a topographic map, much like the ones that Reclamation created when they were planning the Rio Grande Project. Topographic maps use contour lines to represent the shape of the earth's surface. This map uses brown lines to represent elevation in feet. The darker brown lines are marked with a number that represents the elevation above sea level. See if you can find the darker brown lines marked "4000" on either side of the river. Trace these lines with a pencil. They mark where the ground starts to rise and generally represent the boundaries of the valley floor. How would you describe the location of the Leasburg Canal in relationship to that contour line? Why do you think the canal was located there?
3. How many laterals (marked "LAT") can you find? Where do they start? Where do they end? Find the Selden Drain. Where does it begin? Where does it end? How can you tell?
4. This map does not show the smaller drains or laterals. The smaller laterals carry the water to the individual fields that cover the valley floor. Find the areas marked with small green dots. This symbol represents orchards. What kinds of trees are likely to be found here (refer to Reading 3, if necessary).
Click for a larger version ofo Illustrations 1a and 1b.