Inventory-prediction equations describing snowpack water content as functions of readily available or easily obtained inventory variables were developed for use in the ponderosa pine type in Arizona. Although empirical in nature, these equations include parameters assumed to index interception of precipitation inputs, obstruction of direct beam solar radiation, and re-radiation from trees onto the snowpack. Primary consideration was given to forest cover variables in synthesizing the inventory-prediction equations I because currently proposed water improvement programs designed to increase water yield derived from snow consist essentially of vegetative manipulations. Additional independent variables evaluated include potential direct beam solar radiation, elevation, soil, and precipitation inputs. All of the inventory-prediction equations describing a particular snowpack condition were not statistically equivalent in terms of the standard error of estimate or the coefficient of determination. Equations including basal area, bole area I volume, and height-index as expressions of forest cover density were generally better than equations with point density, sum of diameters, and number of trees. Inventory-prediction equations developed to describe snowpack dynamics throughout the accumulation period showed similar statistical form, except as possibly attributable to different precipitation inputs. Equations for characterizing residual snowpacks during spring runoff were statistically weak, possibly because factors other than those considered in this study control the runoff process. The inventory-prediction equations were developed to estimate the mean snowpack water content on a basin, and to describe the trade-off , or the rate of exchange, between snowpack water content and forest-site variables on a decision-making unit. The equations do not necessarily predict changes in recoverable water yield resulting from the implementation of a land management system, however. Nonbiotic characteristics of the land, L e., topographic features, geologic formations, and soil . properties, could conceivably control water yield to the extent that changes predicted by the inventory-prediction equations could be masked. Because of limitations in predicting potential changes in recoverable water yield, it was assumed that a land management system that maximizes snowpack water content on site would also provide the maximum potential for increasing recoverable water yield derived from snow. Management guidelines designed to allow snowpack water content to be maximized on site can be formulated within the framework of the inventory-prediction equations, multiple use management constraints, and forest-based product benefits and costs. Management guidelines indicate that the greatest gain in snowpack water content on site would be realized on decision-making units where the greatest reduction in forest cover density could be prescribed. However, a timber production constraint may limit the array of management possibilities. This constraint was defined as 35 to 40 square feet of basal area or 1,050 to 1,175 cubic feet of volume per acre, depending upon the existing growth percent and the intermingling of tree volumes and size classes. The potential increase in snowpack water content on site will be determined by the magnitude of the reduction in forest cover density and how close management re-direction can approach the timber production constraint. The proportion of the snowpack water content on site converted to recoverable water yield is dependent upon the runoff efficiency.

Interindustry, or input-output analysis is a widely used economic tool in regional analysis. This study investigates the relative worth of alternative types of input data for such models. Primary data are defined as first-hand, or survey data; secondary data are defined as second-hand, or published data. Procurement of primary data is generally much more expensive than for secondary data. Most regional economists have long held that, in general, primary data are superior to secondary data for regional investigations. This study attempts to assess the value of primary versus secondary data in view of the wide variation in collection costs. Two recently published input-output studies for the 1958-60 Arizona economy were utilized to accomplish this goal. One model used mostly primary data; the second model was compiled entirely from secondary data sources. Following careful considerations of base-period differences, geographical overlap, and sector definitions, two models-- the ARZ and the CRB--were constructed from the two source studies so as to be commensurable for statistical comparisons. The ARZ model was derived from the source study that was compiled entirely from secondary data sources; the CRB model was compiled from the source study that used mostly primary input data. Several nonparametric statistical tests were utilized on several components of the ARZ and CRB models to test for statistical similarities and dissimilarities. In general, analyses indicate strong statistical similarity between the two derived models for aggregative I-0 characteristics such as entire matrices and output multipliers, but less similarity for less aggregative components such as sub-matrices and columns of matrices. For example, comparisons between entire technical and between interdependency matrices fail to reject the null hypothesis of no median difference at the alpha level of 5 per cent. At still more unaggregated component analysis, such as for columns within technical and interdependency columns a reasonable degree of statistical similarity persisted. One chapter (V) focuses on the two derived models as they relate to water resources planning implications for Arizona. Results are similar to those for the non-water analyses; however, in the case of weighted water multipliers the similarities between the ARZ and CRB models are remarkably close. Based on an assumed short-run change of 10 per cent in deliveries to final demand for all sectors in the economy, the models differed in predictions of induced aggregate water requirements by only 9000 acre-feet of water, or less than 2 per cent. Results from the study cast doubt on the commonly held assumption of primary-data supremacy in regional interindustry studies. Results also indicate that the most important component for regional economic analysis is the final demand for each sector rather than the interindustry flows. This follows from the narrow clustering of values for output multipliers consistently observed in regional I-0 studies, and reaffirmed in this study. Therefore, students of regional economies are advised to spend marginal resources (money, time, energy) compiling more accurate final demand vectors rather than developing more accurate endogenous interindustry flows.

With groundwater resources becoming less available in the physical, economic, and legal senses, water reuse is rapidly gaining momentum in the arid West. An institutional assessment of water reuse in the Tucson Basin in Arizona indicates that despite institutional changes encouraging the substitution of effluent for native groundwater, many opportunities for water reuse are precluded by existing water rights arrangements and insufficient economic incentives. An economic assessment compares potential benefits and costs of implementing water reuse plans for the Tucson area with potential benefits and costs of alternative water-supply scenarios in which similar quantities of water are provided from other sources. Alternative water sources include pumping native groundwater, "reallocating" water saved through reduction in low value water uses, and importing surface water and groundwater from other basins. The results of this study indicate that at the present time, there is no convincing economic justification for increasing water reuse as planned by the City of Tucson. Not only are reduction in use and importation alternatives less costly to implement than increasing effluent use, they also save more groundwater. The results of the economic assessment indicate that the citizenry of the Tucson Basin would be better served if planned increases in the use of effluent in the Tucson metropolitan area were postponed until the costs become more competitive with the costs of alternatives.

Permanent riparian photopoints (repeat photography of streamside points) are a widely used monitoring method for situations where there are many streams to monitor, and little time to do it. They often display dramatic changes in these dynamic ecosystems – changes that are brought about by management of permitted and non-permitted activities, flood, drought, and fire. Most of all, they help us to learn more about the relationship of riparian areas to uplands, and how riparian ecosystems function.

The availability of adequate and reliable water supplies has always been a critical concern in central Arizona since prehistoric times. The early European settlers in 1868 initially utilized the ancient Hohokam Indian canal system which drew water from the Salt River. However, the river fluctuated with periods of drought and periods of high flows which destroyed the diversion structures. The settlers proposed a dam to store water and to regulate flows. In 1903, the Salt River Water Users Association was formed and an agreement was reached with the U.S. Government for the construction of a dam on the Salt River at its junction with Tonto Creek. The Salt River drains more than 4,306 square miles (mi2) from the White Mountains of eastern Arizona to the confluence with Tonto Creek. Tonto Creek drains a 1,000-mi2 watershed above the confluence. The agreement was authorized under the Reclamation Act of 1902. The Theodore Roosevelt Dam was started in 1905, completed in 1911, and dedicated in 1911 (Salt River Project 2002). The dam has the capacity to store 2.9 million acre-feet (af) of water. However, between 1909 and 1925, 101,000 af of sediment were accumulated behind Roosevelt Dam (Rich 1961). Much of it came from erosion on the granitic soils from the chaparral lands above the reservoir, and much of the erosion was blamed on overgrazing by domestic livestock. Water users were concerned that accelerated sedimentation would eventually compromise the capacity of the dam to hold sufficient water for downstream demands. The Tonto National Forest was originally created to manage the watershed above Roosevelt Dam and to prevent siltation. The Summit Plots, located between Globe, Arizona, and Lake Roosevelt were established in 1925 by the U.S. Department of Agriculture to study the effects of vegetation recovery, mechanical stabilization, and plant cover changes on stormflows and sediment yields from the lower chaparral zone (Rich 1961). The area initially was part of the Crook National Forest which was later added to the Tonto National Forest. The Summit Watersheds consisted of nine small watersheds ranging in size from 0.37 to 1.23 acres (ac). Elevations are between 3,636 and 3,905 feet (ft). The treatments included: exclusion of livestock and seeding grasses, winter grazing, hardware cloth check dams, grubbing brush, sloping gullies and grass seeding. Protection from grazing did not pro duce changes in runoff or sedimentation. Treatments that reduced surface runoff also reduced erosion. Hardware cloth check dams reduce total erosion, and mulch plus grass treatments checked erosion and sediment movement. Runoff was reduced by the combined treatments (Rich 1961). The Summit Watersheds were integrated into the Parker Creek Erosion-Streamflow Station in 1932.

The USDA Forest Service Southwestern Region (FS) manages over 20.5 million acres of forests and grasslands in Arizona, New Mexico and the Texas and Oklahoma panhandles. Water is one of the most beneficial natural resources used on and off these lands by humans, animals and plants. Water on forest and grasslands generally comes from precipitation which arrives in the form of snow or rain, depending on the location and season. On the ground, water infiltrates, ponds, runs off or evaporates, depending on the surface and climatic conditions. In general, precipitation that falls on these lands is free of pollutants. As water moves across and through soils, rocks and other materials it can become polluted by the surfaces it comes in contact with and by materials added to it. Materials added to flowing water in small amounts over time may have little to no harmful effects on the quality of the water. In large amounts and or concentrated, it can be extremely harmful to the quality of the water and users of the water. Common impacts to water quality include increases in temperature, turbidity, nutrient levels and hazardous chemicals. Sources of pollutants on forests and grasslands can be natural and human introduced. Natural sources and causes of pollution can include soil erosion, wildlife waste, concentrations of naturally occurring materials, drought, and flooding. Human sources and causes of pollution can include runoff from roads, trails, tree harvest areas, recreation sites, sewage facilities, livestock, pesticide applications and fuel and chemical spills (USDA Forest Service 2000). A plethora of methods exist to minimize harmful impacts to water quality on forests and grasslands. In 1990, the FS Southwestern Region developed a core set of practices and procedures, that when properly implemented, can be effective at minimizing and mitigating harmful impacts to water quality. The practices and procedures are both administrative and physical, and are collectively referred to as Soil and Water Conservation Practices, also known as Best Management Practices (BMPs) (USDA Forest Service 1990). Even though these BMPs were designed by FS and state resource specialists in the Southwest, they often require adjustments to make them fit site-specific conditions. The BMPs used by the FS Southwestern Region are acknowledged as being effective control measures by the environment departments of the states (Arizona and New Mexico) in which they were developed, as documented in Memorandum of Understandings (MOUs) that exist between the FS and the states.

Dams are structures constructed across rivers to control their flows. The main objectives for building dams are to capture and store the surface flow from rivers and runoff from adjacent and upstream watersheds in artificial lakes or reservoirs and eventually release the stored water as needed. The system may be designed for purposes such as flood control, hydroelectric power generation, and providing freshwater for drinking and irrigation. Reservoirs may also serve as sanctuaries for fish and wildlife and for providing recreational activities such as swimming, fishing, and boating (Colorado River Research Group 2014). However, there are also many drawbacks to building dams that need to be considered. Dams displace people from their homes, flood productive areas, destroy ecosystems and /or impair services, inundate precious historical and cultural artifacts and eliminate important wildlife sanctuaries. The subject of this paper is the Colorado River and the effects of its extensive damming projects on downstream ecosystems and the environment. The Colorado River is the major river in the arid and semi-arid southwestern United States and northwestern Mexico. It is a 1,470-mi (2,352-km) river with its main headwaters in the Rocky Mountain National Park in north-central Colorado. It is the international boundary for 17 mi (27 km) between Arizona and Mexico in the southwest (U.S. Bureau of Reclamation, Lower Colorado Region 2015). The Colorado River system, including the Colorado River, its tributaries, and the lands that these waters drain, is called the Colorado River Basin. It drains an area of 246,000 mi2 (637,000 km2) that includes parts of seven western U.S. states (Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming) and two Mexican states (Baja California and Sonora) (Fig. 1). Three-fourths of the Colorado River Basin is in federal lands comprised of national forests, national parks, and Indian reservations. The drainage Basin's total runoff is about 24,700 ft3 (700 m3) per second (Colorado River Commission of Nevada 2006, Colorado River Research Group 2014). The river is the primary source of water, which comes mostly from snowmelt in the Rocky Mountains, for a region that receives little annual precipitation. For more than a thousand years, the Colorado River has been a central feature in the history and development of the southwestern part of the United States. During this period, management efforts in the Colorado River Basin embody society's struggle to overcome conflicts between competing interests over a shared water resource. First, there have been Native Americans who irrigated their crops with water from the river (Glenn et al. 1996). One tribe, the Cocopah Indians who reside in the delta region fished and farmed there for about 2,000 years. Unfortunately, the present Colorado River is often drained dry by upstream demands before reaching this part of Baja, California (Glenn et al. 1992, Zielinski 2010). In spite of this situation, irrigation is still one of the main uses of the Colorado River, especially on its lower portion where it supports one of the most extensive irrigated agriculture in the United States. Other equally important uses are generating hydroelectric power, and supplying drinking water to distant urban areas and other communities. For example, water from the Colorado River is diverted eastward across the Rocky Mountains to Denver and other cities in Colorado. The Colorado River Aqueduct carries water to the metropolitan area of Los Angeles, California, and the Central Arizona Project brings water supply to the Phoenix and Tucson areas in Arizona. In addition, the cities of San Diego and Las Vegas and many smaller cities, towns and rural communities in Arizona, Nevada, and California are dependent on the Colorado River for their water supply. All together about 35 million people in the U.S. Southwest and 3 million others in Mexico depend on the Colorado River for their water supply.

Ephemeral drainage plant communities of the Sonoran Desert compose a highly significant yet relatively unexplained portion of the ecosystem. Eighty-one percent of all southwestern and 94% of Arizona drainages are categorized as ephemeral drainages (Levick et al. 2008). Small but significant portions of the bajada environment are also composed of ephemeral drainages. These drainages carry out important landscape scale functions in water movement, groundwater recharge, nutrient movement and cycling, sediment transportation, geomorphology, plant habitat, seed disbursement, as well as wildlife habitat and corridors. In decades past, Sonoran Desert bajada research relating the physical earth sciences to ecology has focused on explaining upland plant community patterns along this landform (Yang and Lowe 1956, Phillips and MacMahan 1978, Key et al. 1984, McAuliffe 1994, Parker 1995, McAuliffe 1999). This body of research, however, has very little information pertaining to ephemeral drainages dissecting the upland bajada environment. The bajada geomorphic environment is a composition of geomorphic surfaces of varying soil development proceeding away from a mountain (Peterson 1981, McAuliffe 1994). Each of these geomorphic surfaces is characterized by a unique lithology, slope, age and degree of argillic and caliche soil horizon development. Generally, geomorphic surfaces containing highly developed argillic or caliche soil horizons are found near the mountain while surfaces of undeveloped soils are furthest away from the mountain. Depending on the bajada, local geomorphic history, however, may result in different landscape scale patterns of geomorphic surfaces and soil development. This physical environment forms the template from which the ephemeral drainage develops its channel morphology, hydrology and botanical associations. It was expected that the various geomorphic surfaces composing the bajada found at the study sites would determine the specific channel morphology, hydrology and plant community associations of the examined ephemeral drainage. The goal of this study was to explain (1) channel morphology, (2) hydrology or ephemeral flow patterns and (3) plant communities found along the ephemeral drainage. Plant communities of drainages were also compared to upland communities. These factors were then utilized to give an overall explanation for the distribution of hydrogeomorphic and botanical associations found along the bajada ephemeral drainage.

Stream and watershed restoration projects have become increasingly common throughout the U.S., and the need for systematic post-project monitoring and assessment is apparent. This study describes three stream and watershed ecological restoration projects and the monitoring and evaluation methods employed or planned to evaluate project successes or failures. The stream and watershed restoration and evaluation methods described in this paper may be applicable to projects of similar types and scales. Rivers and streams serve a variety of purposes, including water supply, wildlife habitat, energy generation, transportation and recreational opportunities. Streams are dynamic, complex systems that not only include the active channel, but also adjacent floodplains and riparian vegetation along their margins. A natural stream system remains stable while transporting varying amounts of streamflow and sediment produced in its watershed, maintaining a state of “dynamic equilibrium.” (Strahler 1957, Hack 1960). When in-stream flow, floodplain morphology, sediment characteristics, or riparian vegetation are altered, this can affect the dynamic equilibrium that exists among these stream features, causing unstable stream and floodplain conditions. This can cause the stream to adjust to a new equilibrium state. This shift may occur over a long time and result in significant changes to water quality and stream habitat. Land-use changes in a watershed, stream channelization, installation of culverts, removal or alteration of streambank vegetation, water impoundments and other activities can dramatically alter ecological balance. As a result, large adjustments in channel morphology, such as excessive bank erosion and/or channel incision, can occur. A new equilibrium may eventually be reached, but not before the associated aquatic and terrestrial environment are severely impaired. Stream restoration is the re-establishment of the general structure, function and self-sustaining characteristics of stream systems that existed prior to disturbance (Doll et al. 2003). It is a holistic approach that requires an understanding of all physical and biological processes in the stream system and its watershed. Restoration can include a broad range of activities, such as the removal or discontinuation of watershed disturbances that are contributing to stream instability; installation of control structures; planting of riparian vegetation to improve streambank stability and provide habitat; and the redesign of unstable or degraded streams into properly functioning channels and associated floodplains. Kauffman et al. (1997) define ecological restoration as the reestablishment of physical, chemical and biological processes and associated linkages which have been damaged by human actions.

Hart Prairie is a high-elevation upland riparian ecosystem on the west slope of the San Francisco Peaks in northern Arizona. The location is unique, not only as an upland riparian area in the semi-arid Southwest, but also for having a wet meadow ecosystem dominated by Bebb willow (Salix bebbiana). The ecosystem has experienced a high degree of change since the time of Euro-American settlement. Along with fire suppression, increased wild ungulate herbivory rates, and conifer encroachment into a historically short-grass prairie, several humaninduced changes have been made to the topography of the watershed. Stock tanks, an earthen berm with associated diversion channels, and a road that cuts perpendicularly across the direction of water flow near the base of the watershed have contributed to the altered drainage patterns and the decreased water availability to the flora and fauna in the area. As a result, the Bebb willows and the associated meadow vegetation are at risk. Most of the willows, which constitute the majority of the canopy in the ecosystem, are at a decadent, over-mature stage that allows a limited recruitment of younger plants (Maschinski 1991, Waring 1992). Under these conditions, the plant community may die off leading to the loss of this rare riparian area forever. Research on restoration efforts have been undertaken since the mid-1990s on The Nature Conservancy’s Hart Prairie Preserve and the adjacent US Forest Service Fern Mountain Botanical Area. This paper summarizes the efforts that have been made; most of which targeted to improve the low germination rates of willow seeds, and to restore the geomorphology and surface flow patterns to their pre-disturbance conditions.