Optimization of Operation of Yuma Area Drainage and Regulatory Wells - Pilot Project

Science Center Objects

Reclamation's Yuma Area Office (YAO) operates 50 plus drainage wells and 21 regulatory wells to control groundwater levels in low-lying flood plain areas and to supply a significant portion of the Colorado River water the United States (US) is required by treaty to deliver to Mexico.

Map of facilities along the Colorado River and Yuma Agricultural Area.

Location map showing the location of facilities along the Colorado River and Yuma agricultural area adjacent to the United States-Mexico Border (USBR, 2011).

(Public domain.)

In this era of drought in the Colorado River basin, it is important to maximize the amount of water contributed to the Mexican delivery by these wells. In light of this need, the research question is as follows: What is the optimal subset of drainage and regulatory wells to pump for the next month so as to maximize return flows to the Colorado River, considering all possible options for routing well discharge and subject to these constraints: drawdowns in high water-table areas exceed specified thresholds; projected average annual salinity differential of river water delivered to Mexico at the Northerly International Boundary (NIB) is below its upper limit; salinity of drainage and regulatory water delivered to Mexico at the Southerly International Boundary (SIB) is kept below a maximum limit during the period October-January, when the limit is in effect; pumping of regulatory wells is kept below a specified maximum; and capacities of wells and water conveyance structures are not exceeded?

1. The tool developed in this project should greatly assist YAO in fulfilling its mission requirements to provide adequate drainage relief for farming and other purposes and to deliver Colorado River water of appropriate quantity and quality to all of its customers, including Mexico, in an efficient and rational manner. 

2. In this period of extended drought on the Colorado River, the ability to maximize the portion of the river water supplied to Mexico from pumped drainage and thus potentially reduce the volume of water released from upstream reservoirs is extremely important. 

3. The use of optimization programming with groundwater models is a developing technique which could have applications in the management of other groundwater/surface-water systems in which Reclamation plays a leading role.

YAO collects monthly groundwater-level data from a network of more than 300 wells in the Yuma area. These data can be used to identify the current areas with high groundwater, areas which have the greatest need of drainage pumping.

Current water orders from Mexico are known and future orders can be projected for the rest of the year. The salinity of water in the Colorado River arriving at Imperial Dam is regularly measured and future salinity can be projected for the rest of the year. The flow and salinity of all surface water discharges to the river between Imperial Dam and the NIB are regularly measured and can be projected for the rest of the year. For each drainage or regulatory well, the production rate, salinity, and the possible options for discharging the pumped water are known. Thus for any selected array of wells to pump and routing of discharge, at any given time of the year, the annual average flow-weighted salinity differential can be estimated using actual data up to that time and projected data for the rest of the year.

YAO has a working groundwater-flow model of the Yuma area which is capable of simulating the effects on groundwater levels of pumping the drainage and regulatory wells. The model is now in MODFLOW2000 and will be converted to MODFLOW2005.

With the above indicated data and groundwater flow model, YAO should be able to perform the proposed optimization using either the new United States Geological Survey (USGS) Groundwater Management Process for MODFLOW2005 or an external optimizer, such as GAMS.

In developing the optimization model, YAO will get assistance from the USGS in San Diego, which has expertise in groundwater management optimization.

YAO will share the results of this development by seeking to publish in groundwater and/or water management journals and in Reclamation's operation and maintenance publications.