BOARD00059 ‎(3)‎

• Board Meeting Date: 1/23/2007
• Description: WSP Section - Litigation Account Status Report - Kansas v Colorado, Arkansas Basin Studies and Activities - Colorado River Activities
• Board Meetings - Doc Type: Memo

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This project is being conducted in two regions in the Lower Arkansas River Basin in
Colorado. One region is centered around Rocky Ford (upstream study region - upstream
of John Mal1in Reservoir) and the second region covers the area between Hasty and
Holly. Colorado (downstream study region - downstream of John Martin Reservoir). [n
each of these regions, a number of fields which use different methods of irrigation have
been selected for monitoring. The goal is to monitor an average of three irrigation events
for surt~lce irrigated tields (border and furrow). Flumes and automatic recorders have
been used to estimate the amount of water applied and the amount ofsurf:1ce runoff. With
these data, the amount of water stored in the soil for crop consumptive use and the
amount percolating downward to recharge the shallow water table have been estimated.
Flow meters were used on fields with sprinkler systems to estimate the volume of water
applied during each irrigation. For drip systems, the volume of water applied during the
whole season is used.

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Where appropriate, Parshall, trapezoidal, EZ Flow RampTI\\ and Cutthroat flumes as well
as lUlllouts and weir structures all equipped with pressure transducers and dataloggers
were installed to account for the inflow and outflow volumes of irrigation water entering
and leaving the tields. Data yielded by these devices, once processed and quality
assured/qual ity controlled, generates hydrographs that are used for estimating total
volumes of water applied during an irrigation event. The irrigated areas were mapped
using hand-held GPS units to account for only the portion of the terrain that was watered
during the irrigation event. YSI-30™ conductivity meters were employed for measuring
salinity in both inflow and outflow waters, and random water samples were sent for
laboratory analysis.

Soil electrical conductivity (EC) surveys were conducted two to three times over the
growing season on most of the monitored fields using a Geonics™ EM-38 instrument
(some fields were too dry to conduct all three surveys). The readings obtained using the
EM-38 are associated with soil conductivity and with levels of salinity. The EM-38
readings were geo-referenced using GPS technology, and maps for the different surveys
were generated.

Observation wells were drilled in most of the fields monitored. Between 2 and 5 wells
were installed in most fields in order to observe the variations in water table elevation
throughout the season. YS[-3QTM conductivity meters were employed for the measuring
of salinity and temperature in the water in the monitoring wells.

Rain gauges \vere installed in several of the monitored fields. The rain gauges were
equipped with tipping buckets (Davis instrulllents™ and HOBOTM Event Loggers) and a
datalogger. The rain gauges were calibrated before they were installed in the ticlcls.
Analyses for daily and cumulative precipitation were carried out.

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Two types of atmometers (automatic and manual) manufactured by the ETgage
COlllpllllyTM of Loveland, CO, were utilized for the monitoring of potential
evapotranspiration (ET) in some of the fields, Each field was monitored individually for