The MAC Region IRWM Program coordinates water resource planning and activities across Amador, Calaveras, and Alpine Counties in California. The region was established under California's Integrated Regional Water Management program to promote sustainable water use, reliable supply, environmental protection, and a strong economy. The Upper Mokelumne River Watershed Authority now leads the MAC region and has established committees for governance and stakeholder involvement.

1. MAC Region IRWM Program
California has established a state-wide Integrated Regional Water Management (IRWM)
Planning program that promotes collaborative planning and prioritized water resource
management actions in regions throughout the state. The program’s goal is to systematically
ensure sustainable water uses, reliable water supplies, better water quality, environmental
stewardship, efficient urban development, protection of agriculture, and a stronger regional
economy. Administered by the California Department of Water Resources (DWR), the state
IRWM program encourages creation of Regional Water Management Groups (RWMG) and the
use of collaborative processes to develop integrated regional water management plans which
target regional water resource issues. DWR supports and promotes the integrated regional
planning work of RWMGs by providing funding through competitive grants.
The initial MAC IRWM planning effort was initiated as a cooperative effort by Amador Water
Agency (AWA), Calaveras County Water District (CCWD), Amador County, City of Jackson,
City of Sutter Creek, City of Plymouth, Amador Regional Sanitation Authority (ARSA) and East
Bay Municipal Utility District (EBMUD). These entities entered into a Memorandum of
Understanding (MOU) for the purposes of coordinating water resources planning and
implementation activities and formed the official MAC region RWMG, with AWA assuming the
role of region administrator for the RWMG. The initial MAC IRWM was adopted in November
2006.
In 2009 the Upper Mokelumne River Watershed Authority assumed lead agency responsibilities
with respect to the MAC Region IRWM program. In fulfilling this RWMG role UMRWA has
established two committees, the Board Advisory Committee (or BAC) and the Regional
Participants Committee (or RPC). The BAC is comprised by UMRWA directors representing
Amador water Agency, Calaveras County Water District and East Bay MUD. The RPC is
discussed under a separate link on this webpage.
What is MAC?
MAC is an acronym for Mokelumne-Amador-Calaveras. The term was coined to describe the
MAC region, one of more than fifty IRWM regions established in California under the state’s
IRWM program. The MAC region incorporates all of Amador County and sizeable portions of
Calaveras and Alpine Counties. Included within the region’s boundary are cities, water and
irrigation districts, watershed management areas, portions of groundwater basins, disadvantaged
communities, and large tracts of federally-owned lands. Figure 1 shows the MAC IRWM region.
The MAC region contains approximately 1.25 million acres (about 1,950 square miles) and is
located in the Sierra Nevada foothills, approximately 45 miles southeast of Sacramento. Situated
in a transitional zone between the San Joaquin Valley and the Sierra Nevada, the region stretches
across varied topography and microclimates. Warm, dry summers and mild winters are
predominant in the western foothills. Mild summers and cold winters characterize the
mountainous eastern region with temperatures ranging. Hot, dry summers and mild winters
prevail in the western portion of the region with summer day time highs in excess of 100
degrees.
The MAC IRWM region is home to approximately 130,000 people. About 80% of the population
lives in urban areas, although 98% of the region is considered rural. The overall population

2. density is 2000 people per square mile (the average for the entire region), with rural areas having
a population density of about 40 people per square mile.
The primary sources of water in the region are the Mokelumne and Calaveras River watersheds
(and to a lesser extent, the Cosumnes River watershed), with snowmelt and rainfall from the
Sierra Mountain
Range transported via the rivers and their tributaries. Although the region is famous for its
historic gold mining and recreation, current land uses also include cattle ranching, orchards,
timber, vineyards and row crops, and mining (industrial minerals, limestone, sand and gravel).
Development in the MAC Region, both urban and rural, is clustered around the major cities and
highways. Agriculture, grazing, and open spaces dominate land uses and represent a relatively
large portion of the total region land use. Other industries outside the urban setting include
mining and timber harvesting where the majority of the land cover is forest, shrub and grassland.
General land use trends in the region include significant development of rural and agricultural
areas associated with population increases in Plymouth and Sutter Creek (Amador County),
Kirkwood and Bear Valley (Alpine County), and the Rancho Calaveras and La Contenta areas
(Calaveras County). A second land use trend is a shift from grazing to viticulture and viticulture
to residential development.
FIGURE 1: