Projects by Discipline / Water Resources Planning and Management

Pecos River Adjudication
Settlement and Compact Compliance

The Pecos River Adjudication Settlement is one of several ongoing Hydrosphere projects in the Pecos basin. The State of New Mexico’s Interstate Stream Commission (ISC) retained Hydrosphere in 2000 to assist them with a variety of technical, regulatory, and political water management problems.

Since the U.S. Supreme Court’s 1988 Amended Decree ruling on the Pecos River Compact, New Mexico has achieved compliance largely through short-term leasing of irrigation water rights. In 2001, faced with the prospect of a potential compact delivery shortfall and the possibility of a priority call, the ISC formed an ad hoc committee comprised of water users and stakeholders in the Pecos River basin to develop a long-term solution to the Compact compliance problem. These discussions led to the Adjudication Settlement agreement, signed in March 2003.

During the settlement negotiations, Hydrosphere provided technical support for evaluation of the proposed settlement terms. A decision support system comprised of three computer models and numerous data processing and accounting tools was developed to assist these negotiations. The system consists of a surface water and reservoir operations model developed in RiverWare™ and two MODFLOW models of the Carlsbad and Roswell groundwater basins.

The settlement agreement anticipates retirement of various irrigated lands and their associated surface and groundwater rights. The models were used to evaluate the probable yield from these retirements as they accrue to downstream water users and to the state line.

Since the signing of the agreement in 2003, Hydrosphere’s participation in the settlement process has evolved to include:

• Preparation of several expert reports submitted for use in related litigation
• Evaluation of water rights for potential purchase, including yield analysis and consumptive use transfer issues
• Development of accounting tools to facilitate tracking water ownership
• Representation of the state in ongoing NEPA EIS programs required for re-authorization of storage uses for purchased water rights in the Carlsbad Irrigation District