The Newlands drains that supply “Carson Lake and Pasture” as well as Stillwater National Wildlife Refuge are an obvious source of water quality problems. Water in drains comes from farm run-off and shallow groundwater (Newlands Shallow Ground Water is next). Precipitation is probably inconsequential. During years with abundant water, water may be “spilled” from Lahontan Reservoir to control water levels. This water is generally routed down the canals. If the water supply approaches unmanageable levels, the Truckee-Carson Irrigation District offers “spreading” (Truckee-Carson Irrigation District, 2010, p. 1-13), whereby anyone with the necessary conveyance who wants water can get it even if the annual delivery ultimately exceeds the recipient’s water rights. Like normal farm run-off, some of this water ends up in drains. This happened in 2023 (www.nevadaappeal.com/news/2023/mar/24/residents-warned-of-spring-flooding-in-churchill-county/?LVN%20(lahontan-valley).
Farm run-off is the water that flows off of an irrigated field without sinking into the ground or being taken up by plants. Unlike sprinkler systems or even furrow irrigation, the flood irrigation practiced on 99% of the Newlands Project in 2009 (Truckee-Carson Irrigation District, 2010, p. 1-2) ensures that there will be run-off. I have not found any chemical analyses of run-off or any estimates of the amount of run-off. In any case, this water starts out with the quality of the Carson River below Lahontan Dam. It is subject to evaporation as it travels down canals to the field to be irrigated. It exchanges chemical constituents with the soil it flows across. The soil is weathered Fallon formation or Lahontan Valley group sediments.
A 1935 report by an agronomist with the U.S. Department of Agriculture, W.E. Knight, provided a host of information on weather, growing seasons, possible crops to plant, the best variety of crops to plant, yields obtained at the Fallon Agricultural Field Station, and animal husbandry. He also described soil conditions:
- “[T]he soils of the region often contain appreciable quantities of soluble salts, the heavier soils, or fine clays, containing greater quantities than the fine sands or coarser material . . . The soils over the entire area of the project contain more or less of the salts of sodium” (Knight, 1935, p. 2).
That’s bad for growing crops.
Knight (1935) described ways to remove the “salts”.
- What is needed “is a movement of the irrigation water applied downward through the soil so that the soluble salts may be removed” (p. 11).
- Or, if the soil has mineral efflorescence or other indications of “soluble salts”, relatively high flow rates should be employed “to wash off the surface accumulations of salt, thus avoiding penetration as much as possible” (p. 12).
- One method of soil improvement is to disk manure into the soil and flood irrigate every 2 weeks and to subsequently not plant a crop but to use shallow cultivation to control vegetation. “During this period the application of water should be copious, as the removal of the harmful salts depends on the leaching effect of the water” (p. 15). Depending on soil conditions, a crop could be seeded the next year after more manure and disking or the first year’s method could be repeated (p. 15).
- Another method is to spread 7.6-10.2 cm (“3 or 4 inches”) of sand on top of an “adobe soil” to provide a seed bed (p. 16).
- For “changing of the more toxic alkaline salt into one of the less toxic forms, e.g., sodium carbonate to sodium sulfate”, gypsum could be applied to the field (p. 12). Sulfur or alum could also be used, with or without gypsum.
- Sulfuric acid could be added directly to the irrigation water. “The use of this acid proved to be effective but relatively expensive” (Knight, 1935, p. 13).
- Spreading alum over an impermeable soil and then keeping it flooded for 24 hours improved the permeability “making it possible to obtain a fairly uniform stand of alfalfa” (p. 14).
Knight’s (1935) descriptions indicate that farm run-off is likely to have high concentrations of sodium and bicarbonate or carbonate ions from the dissolution of sodium carbonate and of the constituents of whatever the other “soluble salts” are, at least initially. Run-off might also contain the products of soil treatments but I haven’t found any information on that.
Because irrigated acreage for the entire Newlands Project was estimated to be 210 square km (“52,000 acres”) in 1948 (Hoffman, 1994, p. 9) and this is close to the 237 square km (“58,669 acres”) of the Carson Division irrigated 60 years later in 2009 (Truckee-Carson Irrigation District, 2010, p. 1-1), most of the easily leached soil constituents may already have been washed off.
Glancy and Katzer (1976, p. 86) quoted a description of water quality of the Newlands Project as of 1960 from Rollins (1965, Water quality of the Newlands Reclamation Project: U.S. Dept. Agriculture, Agricultural Research Service Paper ARE 41-97, 44 p.). It includes the following statements:
- “(2) the drainage waters are higher in dissolved solids and percent sodium than the irrigation water;
- “(3) drainage waters further increase in salt concentration as they flow downstream;
- “(4) drains in the center of the project, particularly south of the Carson River, are free from excessive salt but pick up salt rapidly as they approach the Carson Lake and Carson Sink areas;
- “(5) conversely, drains immediately north of the Carson River carry high salt concentrations;
- “(12) chemical quality of the irrigation water supply probably has not changed since the project began (1905), but the quality of drainage water has probably improved over the long term (that is, greater quantities of salt were removed by drainage water during early years of the project than are being removed now).”
“Drainage waters” probably include both farm run-off and shallow ground water. They may be mostly run-off during the irrigation season and mostly ground water during the off season. “Salt” may refer to TDS rather than to halite or to Knight’s (1935) “soluble salts”, whatever they were.
At a minimum, farm run-off is likely to have higher concentrations of most constituents than Carson River water due to evaporation. It may pick up sodium and bicarbonate or carbonate to the extent the “salts of sodium” have not been thoroughly leached from the soil. Accounting only for evapotranspiration and not for mineral dissolution or precipitation and assuming that canal water has a TDS concentration of 180 mg/L, Herrera and others (1999, p.60) estimated that the TDS of water available to recharge ground water is 550 mg/L. This final result includes all the evapotranspiration that occurs on the field so 550 mg/L is an estimated upper limit for the TDS concentration of farm run-off.
The chemistry of drain water is considered after a review of ground water quality in the next section.