Arlington Basin Groundwater Sustainability Plan

Customer Profile

The Western Municipal Water District (WMWD) provides water, wastewater, and recycled water services to almost 1 million people, including more than 23,000 retail water customers and 130 irrigation customers across 527 square miles in western Riverside County, California.

Challenge

The Arlington Basin was designated as very low priority and thus was not required to develop a GSP. However, being committed to good basin management, the WMWD didn’t take advantage of this loophole, but instead decided to continue meeting with stakeholders to establish a 14-month, 5-step plan to develop a GSP.

1. Establish a governance structure to manage and enforce the plan
2. Document the basin geology, groundwater use, and all factors affecting future groundwater demand and management
3. Set measurable sustainability goals and the systems to monitor progress
4. Develop the plan by identifying the projects and management actions required
5. Adopt the plan

Once the WMWD completed step one and had a governance structure in place, they looked for a partner to assist in creating the plan.

Geoscience Solution

Prior to this project, Geoscience began developing the Santa Ana River Integrated Model to combine nine ground and surface water models into one integrated model for the entire upper watershed, including the Riverside-Arlington Basin.

Consequently, the District turned to Geoscience and the Integrated Model to deliver, or provide guidance for, the development of water budgets and assessment of proposed groundwater projects as part of the process of establishing a GSP. 

Specifically, Geoscience used the Integrated Model to assess the basin’s current and historical conditions, provide a detailed basin characterization, develop the water budget, assess sustainable management criteria, and determine the effectiveness of proposed projects and management actions. 

Customer Results

Being well acquainted with the requirements of SGMA, the Geoscience team worked in conjunction with the District to complete all of the studies and investigations required to complete a compliant GSP, including supporting grant administration and stakeholder engagement, responding to public comments, assessing and developing a data management system, reviewing monitoring networks and providing recommendations, defining the plan area, and preparing the submittal documents.

The deliverables included:

• Grant administration and support
• GSP components
• Plan area and basin setting
• Hydrogeologic conceptual model, groundwater flow modeling, and water budget
• Management goals and objectives
• Monitoring network
• Environmental compliance and permitting
• Cost of schedule and Implementation
• Stakeholder outreach
• Monitoring well planning, evaluation, design and construction, and monitoring plan

Once the GSP completes the review cycle, Geoscience will assist the District in revisions, if required, and then implementation of the plan.