This section summarizes beneficial and adverse impacts to surface water quality and quantity, and groundwater quality and quantity. In addition, the section describes the differences between direct and indirect impacts and short- and long-term impacts.
Adverse impacts to water quality are those that result in a violation of state water quality standards or degrade a designated use. Management actions that permit surface-disturbing activities that contribute to offsite erosion and sediment delivery are considered adverse impacts. Beneficial impacts to surface water quality result from management actions that improve water quality or minimize, reduce, or prevent offsite erosion or the discharge of supplemental water that is of lower quality than the ambient water quality of the receiving water. For example, management actions that stabilize watershed projects no longer meeting resource objectives or that seed degraded portions of watersheds would result in beneficial impacts to surface water quality.
Direct impacts to surface water quality are those that degrade the ambient water quality of surface waters in the Planning Area. For example, management actions that modify drainages, such as altering the number of linear water crossings or the distribution and condition of wetlands and riparian areas, would result in direct impacts to surface water quality. Indirect impacts are those that disturb soil in a watershed, especially highly erodible soil, as this leads to increased sedimentation.
Long-term impacts to surface water quality are those that result from bare soil or established point discharges that increase sediment loads or degrade water quality. Short-term impacts include exceedances of state water-quality standards mitigated within required timeframes, or surface disturbances temporarily affecting water quality that are reclaimed immediately after a temporary use.
Impacts to surface water quantity result from management actions that reduce or supplement streamflows and may be either beneficial or adverse, depending on the quantity and the location of the withdrawal(s) and/or discharge(s).
Direct impacts to surface water quantity result from management actions (e.g., vegetative and physical treatments, impoundments, retention and detention structures, etc.) that increase or decrease runoff, as well as from changes in the quantity of produced water discharged into the system. Direct impacts also result from adding or modifying diversions from the drainage system.
Indirect impacts to surface water quantity result from management that modifies the capacity of stream channels or result in changes to the amount of water reaching the stream system. For example, changes in the locations of roads that direct surface water runoff into drainages may increase or decrease the timing and amount of surface water flowing in the stream system. The distribution and condition of wetlands and riparian areas would indirectly result in changes to surface water quantity because they increase infiltration and delay peak flows.
Long-term impacts to surface water quantity are those that alter the amount of impervious surface in a drainage or change established discharges that alter supplemental streamflows (more than 5 years). Short-term impacts include uses that may temporarily affect water quantity, such as temporary impoundments or detention structures.
Change in the number of wells drilled in a given area, including domestic or municipal water supply wells, oil and gas wells, and water disposal or injection wells, result in direct impacts to groundwater quality and quantity. Other factors include the number and location of springs developed, whether there are water conservation efforts in an area, and the amount of water infiltration and recharge. Oil- or gas-well stimulation methods also can directly affect groundwater.
Indirect impacts to groundwater quality and quantity result from activities that modify recharge areas related to a groundwater system or systems. For example, activities that decrease vegetative cover, or increase runoff, can reduce infiltration of precipitation, thereby reducing recharge to groundwater aquifers.
Short‐term impacts to groundwater are those resulting from any temporary or short-term use of groundwater—for example, temporary use of a well to supply water for drilling an exploratory gas well or for supplementing the water supply in a grazing allotment. Long‐term impacts to groundwater quality and quantity can result from permanent oil and gas fields and production facilities constructed in recharge areas, or from landscape alterations that modify groundwater recharge. Such impacts can include wells that deplete an aquifer through extraction of water, paved surfaces and compacted soils that decrease water infiltration, or wells used to inject water of similar quality (disposal wells) into the aquifer.