**National Irrigation Water Quality Program**\
U.S. Department of the Interior

Concentrations, Loads, and Yields of Potentially Toxic Constituents in
Irrigation-Drain Systems, Newlands Project Area, Carson Desert, Nevada,
November 1994-October 1995

Michael S. Lico and R. Nyle Pennington\
U.S. Geological Survey

ABSTRACT

The U.S. Geological Survey National Water-Quality Assessment Program, in
cooperation with the U.S. Department of the Interior National Irrigation
Water Quality Program, investigated the chemical characteristics of
water and bottom sediment in irrigation drains in the Newlands Project
area near Fallon, Nevada. The purpose of the investigation was to
determine loads of contaminants potentially toxic to wildlife that
irrigation drains contribute to wetland areas and to identify specific
areas that contribute the greatest yields. Water and bottom-sediment
samples were collected and flow was measured at 22 sites in the Newlands
Project during 1995. Water samples were analyzed for major and trace
constituents, nutrients, and pesticides. Bottom-sediment samples were
analyzed for major and minor elements. In addition, flow and specific
conductance were measured at 150 other drain sites and used, on the
basis of relations between dissolved solids, boron, and specific
conductance, to estimate loads of dissolved solids and boron delivered
by the drain systems.

Concentrations of most constituents were greater for samples collected
during the nonirrigation season (November-March) than those during the
irrigation season (April-October). Arsenic, boron, molybdenum, and
dissolved-solids concentrations commonly exceeded beneficial-use
criteria for water in wetlands.

In general, estimated loads of dissolved solids, boron, and arsenic were
greater during the irrigation season than during the nonirrigation
season. The Lower Diagonal Drain system transports the largest loads of
dissolved solids, boron, and arsenic to the Stillwater National Wildlife
Refuge (NWR) wetlands, Large loads of these constituents also were
delivered to the Stillwater NWR wetlands by the Harmon and Stillwater
Slough-Kent Lake Drain systems. Drain systems that empty into the Carson
Lake wetlands (Carson Lake and L) deliver approximately equal loads of
dissolved solids as well as equal loads of arsenic to these wetlands.
The L Drain system annually delivers almost twice as much boron as the
Carson Lake Drain system to the Carson Lake wetlands. About three times
as much dissolved solids were delivered to the Stillwater NWR wetlands
than to the Carson Lake wetlands during the period of load estimates
(November 1994 through October 1995).

Five specific areas were identified as the greatest contributors of
potentially toxic constituents to the drain systems. These areas are
parts of the Harmon, Stillwater Slough-Kent Lake, Lower Diagonal, Carson
Lake, and Soda Lake Drain systems.

The estimated yields of dissolved solids, boron, and arsenic (tons per
acre) for the year ending October 31, 1995, differed greatly among drain
systems in the Newlands Project. Areas drained by the TJ and Harmon
Drain systems had the highest yields of dissolved solids and boron. The
lowest yields of dissolved solids and boron were from areas drained by
the New River and Carson Lake Drain systems. Estimated yields of arsenic
were greatest from areas drained by the TJ Drain system, and also were
high for areas drained by the Lower Diagonal and Harmon Drain systems.
Arsenic yields were lowest from areas drained by the New River Drain
system.