Mokelumne/Amador/Calaveras (MAC) IRWM (planning stage)
The Mokelumne/Amador/Calaveras Regional Integrated Water Management Plan was formed in 2006 to: foster coordination, collaboration and communication among regional and local agencies responsible for water-related issues; achieve greater efficiencies in project development and implementation; build public support for vital projects; identify the most important water-related projects according to a set of criteria; improve regional competitiveness for project funding. An Integrated Regional Water Management Plan (IRWMP) was developed for the region to identify projects and measures to be implemented to meet these goals.
To learn more about the MAC IRWM group, please visit the MAC IRWM website here.
The M/A/C IRWMP region incorporates all of Amador County and sizeable portions of three other counties – Calaveras, San Joaquin, and Alpine, as well as several cities and water management organizations. The approximately 1.25 million acre region (about 1,950 square miles) 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 with temperature ranging from the middle 30s to the high 90s (in degrees Farenheit). Mild summers and cold winters characterize the mountainous eastern region with temperatures ranging from the low 20s to the middle 80s. Hot, dry summers and mild winters prevail in the Central Valley portion of the region with temperatures ranging from middle 30s to highs in excess of 100 o F. The primary source of water in the region is 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 mining and existing active mines (asbestos, gold, industrial minerals, limestone, sand and gravel), current land uses also include cattle ranching, orchards, timber, vineyards and row crops.
The M/A/C IRWMP region was formed using physical, political and social boundaries. The Mokelumne River watershed forms the eastern border, while the Calaveras River watershed forms the southern boundary. The Amador County boundary generally follows the Mokelumne watershed boundary and roughly defines the northern border. The southwestern boundary of the region extends to Interstate Highway 5 (I-5) in San Joaquin County, encompassing an aquifer storage and recovery (ASR) project, a conceptual project identified as part of this plan. This region was defined based on similar water supply and demand characteristics and the opportunities to facilitate water resources protection, development and security.
The M/A/C IRWMP region is a largely natural area with much of it designated as rural or open space. There is an abundance of water features in the form of rivers, creeks, ponds, lakes, and reservoirs. As such, the region provides a great deal of varied habitat for numerous species. The Upper Mokelumne River has been designated as a scenic waterway. There are a number of special status biological species in the M/A/C IRWMP region and many listed in the 08/06 California Natural Diversity Database designated as “Threatened” or “Endangered”. Additionally, there are several “Special” animal and plant species in the M/A/C region that have been designated as such by either the California Department of Fish and Game or the California Native Plant Society due to declining population levels, limited ranges and/or continuing threats that make them vulnerable to extinction.
The topography of the M/A/C IRWMP region varies greatly. The western edge of the region is in the Central Valley, west of Lodi, and is very close to sea level. The eastern edge of the region is in the Sierra Nevada mountain range at the headwaters of the Mokelumne River at an elevation well over 9,500 feet. The terrain from east to west becomes gentler as the mountains and foothills give way to the Central Valley. The topography of the region has defined multiple watersheds within the region. The two watersheds (Mokelumne and Calaveras) that dominate the region are described below.
MOKELUMNE RIVER WATERSHED
The Mokelumne River originates in the Sierra Nevada and flows west to its confluence with the San Joaquin River in the Central Valley. With a watershed encompassing approximately 660 square miles, the annual average runoff of the Mokelumne River at Pardee Reservoir is 753,000 acre-feet, with the majority of flow derived from snowmelt. Annual precipitation and streamflow in the Mokelumne River is extremely variable both month to month and year to year. Stream flow is modified by upstream diversions and regulated by reservoir storage operations for hydroelectric power generation and water supply. The Mokelumne River watershed is typically subdivided into the Upper Mokelumne River Watershed, extending from its upper reaches in eastern Alpine County to the southwestern side of Pardee Reservoir, and the Lower Mokelumne River watershed, extending from its shared boundary with the upper watershed, southwest through the river’s confluence with the Cosumnes River. As the Mokelumne River traverses the foothills to the Central Valley, the Mokelumne River and its
tributaries pass through several lakes and reservoirs, including Amador Lake, Henderson Reservoir, Lower Bear River Reservoir, Mosquito Lake, Tiger Creek Reservoir, Salt Springs Reservoir, Pardee Reservoir, and Camanche Reservoir. Early settlers used the Mokelumne River during the second half of the 19th century for mining, hydropower development, and steamboat transportation. The most notable effect on the river, however, resulted from mining activity following the discovery of gold in 1848 and copper in 1861. Gold mining in the Mokelumne River watershed peaked in 1854, and declined steadily thereafter. Copper was discovered in 1861 and mined heavily between 1899 and 1919. Mine effluent discharged into the river eliminated all downstream aquatic life, including salmon runs, in 1943 and 1944. Today, the Mokelumne River is used as a water supply for AWA, EBMUD, and other local water districts and agencies. PG&E and EBMUD also use the river for hydroelectric development. Restoration activities began on the river in 1992 to improve the impacted aquatic community, resulting in increased salmon runs over the past few years. The watershed is also owned, and managed, by a variety of public and private entities. Notable landowners in the Mokelumne River watershed include the U.S. Forest Service, Sierra Pacific Industries, and PG&E.
Upper Mokelumne River Watershed
As previously noted, the Mokelumne River originates in the Sierra Nevada and flows west to its confluence with the Cosumnes River. The upper portion of the Mokelumne River watershed lies predominantly within the 105,165 acre Mokelumne Wilderness. The Mokelumne Wilderness, a federal wilderness area protected under the Wilderness Act of 1964, straddles the crest of the central Sierra Nevada, within the Stanislaus, El Dorado, and Toiyabe National Forests as well as portions of Calaveras, Alpine, and Amador Counties. Watersheds within the Mokelumne Wilderness area drain to the Mokelumne River on the west slope and the Carson River on the east slope. The Upper Mokelumne River watershed is defined as all lands that drain into the North Fork, Middle Fork, South Fork, and Main Stem of the Mokelumne River with the southwestern edge of Pardee Reservoir as the downstream boundary. This approximately 550 square mile watershed is located within Alpine, Amador and Calaveras Counties. The North Fork watershed is the largest tributary at 370 square miles and contributes 85% of the river flow. The Upper Mokelumne River watershed topography is rugged, with elevations ranging from 600 to 10,400 feet. The watershed contains important habitat for sensitive species, is used by outdoor recreation enthusiasts throughout the year, and is the source of drinking water for people living in and outside of the watershed. Land and water resource management decisions in the watershed are made by a variety of public and private entities, including the U.S. Forest Service, Sierra Pacific Industries, EBMUD, and PG&E. To address areas of mutual concern pertaining to water supply, water quality management and the preservation of the environment within the Upper Mokelumne River watershed, the Upper Mokelumne River Watershed Authority (Authority) was formed under a joint powers authority in 2000 to undertake watershed assessment and planning projects. Members of the Authority include Alpine County Water Agency, AWA, CCWD, CPUD, EBMUD, JVID, and Alpine, Amador and Calaveras Counties.
Lower Mokelumne River Watershed
The Lower Mokelumne River watershed encompasses 80 square miles and flows from Highway 49 to the River’s confluence with the Cosumnes and San Joaquin Rivers. The watershed for the Lower Mokelumne River includes portions of Amador, Sacramento and San Joaquin counties, the lower edge of Pardee Reservoir, Camanche Reservoir, and the confluence of the Cosumnes and Mokelumne Rivers. The Lower Mokelumne River is used heavily for water supply, hydroelectric generation and recreation, and, at the same time, contains a broad and diverse array of environmental habitats. Habitats along the lower river, especially at its confluence with the Cosumnes River, are considered to support some of the most significant valley floodplain forests and wetlands remaining in the Central Valley. Like the Upper Mokelumne River, land and water resource management decisions are made by a variety of entities including the U.S. Fish and Wildlife Service, the U.S. Bureau of Land Management, Sacramento and San Joaquin Counties, and EBMUD. A non-governmental organization involved in the management of the Lower Mokelumne River is the Mokelumne Cosumnes Watershed Alliance. The Mokelumne Cosumnes Watershed Alliance is an alliance of many organizations interested in management of the lower Cosumnes and Mokelumne Rivers, and includes the California Department of Water Resources, California Department of Fish and Game, EBMUD, San Joaquin and Sacramento Counties, NOAA Fisheries, and the Sacramento Area Flood Control Agency, as well as many others. The study area for this organization includes a 17-mile reach of the Mokelumne River from the Woodbridge Irrigation District Dam downstream to Lost Slough, and a 28-mile reach on the Cosumnes River from the Folsom South Canal downstream to the confluence with the Mokelumne River.
CALAVERAS RIVER WATERSHED
The Calaveras River watershed drains approximately 470 square miles of land above the foothill line in Calaveras and San Joaquin Counties. The Calaveras River watershed is atributary to the San Joaquin River Delta system and is located in Calaveras, Stanislaus, and San Joaquin counties. The majority of the watershed lies in the northwestern region of Calaveras County with the western-most portion of the watershed in San Joaquin County and a small, southwestern area falling
within the Stanislaus County border. Like the Mokelumne River, the Calaveras River watershed may be divided into the Upper Calaveras River watershed and the Lower Calaveras River Watershed, with the dividing line occurring just west of New Hogan Reservoir. Flow in the Calaveras River is primarily derived by rainfall with almost no contribution by snowmelt. New Hogan Dam was constructed on the Calaveras River in 1963 for flood control, and municipal, industrial and irrigation purposes, and releases from New Hogan Dam currently control flows on the Lower Calaveras River. The upper watershed above New Hogan reservoir covers 363 square miles with an average annual runoff of about 166,000 acre-feet. The Lower Calaveras River – Mormon Slough area is below New Hogan Dam.
The watershed for this portion of the river encompasses approximately 115,000 acres and receives up to 90,000 acre-feet of surface water supply from the Calaveras River. The four main tributaries below New Hogan are Cosgrove Creek, South Gulch, Indian Creek, and Duck Creek. Cosgrove Creek provides the largest run-off contribution to the Calaveras River, which has been as much as 8,500 acre-feet in some years. As with the Mokelumne River, land and water resource management decisions for the Calaveras River are made by a variety of entities, including many of the same organizations as for the Lower Mokelumne River. One additional organization involved in the preservation and management of the Calaveras River is the Calaveras River Watershed Stewardship Group. They focus on the lower Calaveras River below the New Hogan Dam. Members of this group include the U.S. Fish and Wildlife Service, the California Department of Fish and Game, Stockton East Water District, Calaveras County Water District, NOAA Fisheries, California Department of Water Resources, City of Stockton, and California Department of Conservation