Water Management

Units: m³/s, L/s or depth-equivalent mm

Short description: The extent of impermeable surfaces in urban areas is continually increasing as cities develop and expand, due to the construction of buildings, roads, streets, parking lots, etc. A significant consequence is greater runoff in urban areas, which can also lead to flooding. Direct measurement of runoff (and its characteristics) can be performed using standard approaches, including weirs, pressure transducers/loggers, tipping-bucket gauges, etc.

Units: mm

Short description: The extent of impermeable surfaces in urban areas is continually increasing as cities develop and expand, due to the construction of buildings, roads, streets, parking lots, etc. A significant consequence is greater runoff in urban areas, which can also lead to flooding. USDA Curve Number method takes into account losses (interception, infiltration and storage) as well as antecedent moisture conditions – runoff is estimated for storm events. The most widely used modelling method to estimate runoff from rainfall. Particularly useful for comparing pre- and post-development peak rates, volumes, and hydrographs. CN values are function of soil, hydrological conditions and landcover (can be weighted).

Units: m³/s or L/s

Short description: The extent of impermeable surfaces in urban areas is continually increasing as cities develop and expand, due to the construction of buildings, roads, streets, parking lots, etc. A significant consequence is greater runoff in urban areas, which can also lead to flooding. Rational Method is used for estimating ‘peak’ flow rates for simple urban watersheds/sewers and is often used for design discharges. Requires rainfall intensity, the runoff-coefficient (can be derived from published value) and watershed area.

Units: m³/s or L/s

Short description: The extent of impermeable surfaces in urban areas is continually increasing as cities develop and expand, due to the construction of buildings, roads, streets, parking lots, etc. A significant consequence is greater runoff in urban areas, which can also lead to flooding. IDF analysis provides a convenient tool for summarizing regional rainfall information and thus it is useful in municipal stormwater management practices.

Units: mm

Short description: The extent of impermeable surfaces in urban areas is continually increasing as cities develop and expand, due to the construction of buildings, roads, streets, parking lots, etc. A significant consequence is greater runoff in urban areas, which can also lead to flooding. One-dimensional and two-dimensional drainage system modelling exist. There are many examples of models applied in an urban context which are listed here. Impact of climate change on runoff can be evaluated using the design storms. The models typically require multiple parameters for accurate results.

Units: % or mg/L

Short description: Total Suspended Solids (TSS) are solids in water that can be trapped by a filter. TSS can include a wide variety of material and can have adsorbed pollutants. High concentrations of suspended solids can affect the health and productivity of the aquatic life. Total suspended solids (TSS) are typically quantified in the laboratory using a gravimetric process, yielding TSS measurement in units of mass per volume (e.g., mg/L or ppm). Measurement of TSS involves filtration of a water sample followed by drying and weighing of the particulates removed.

Units: % (as total load and/or reduction)

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Nutrients, including nitrogen (N) and phosphorus (P), can have significant impact on water quality, including effects on plant growth, oxygen concentration, water clarity, and sedimentation rates. Some major anthropogenic sources of nutrients are agricultural and industrial emissions, discharged wastewater and atmospheric deposition. Nitrogen and phosphorus are present in water in many different forms, or as many different chemical species. The forms of N and P that are quantified can include some or all of the following:

• •    Nitrogen: total N (N_tot), total Kjeldahl N (TKN), dissolved organic N (DON), nitrate (NO₃^-), nitrite (NO₂^-) and ammonia/ammonium (NH₃/NH₄⁺)
• •    Phosphorus: total P (P_tot), acid-hydrolysable P (AHP), orthophosphate (PO₄^3-)

Different nitrogen and phosphorus species can be quantified in a water sample either in the field, using a test kit or ion selective electrode (ISE), or via laboratory analyses. Laboratory analyses can be done for multiple chemical species of N and P.

Units: % (as total load and/or reduction)

Short description: Metals and metalloids (herein referred to simply as metals) are ubiquitous in the natural environment and can potentially accumulate to toxic levels for the aquatic environment and humans as metals do not degrade with time. As such, metals can have a significant impact on water quality and its fit-for-purpose use. Some of the more common metal pollutants are: aluminium (Al), arsenic (As), barium (Ba), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), molybdenum (Mo), nickel (Ni), lead (Pb) and mercury (Hg), selenium (Se), vanadium (V) and zinc (Zn).

Units: CFU/100 mL or CFU/100

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Faecal coliform bacteria are a subgroup of a larger total coliform group referring to the Gram-negative, rod-shaped bacteria. Faecal coliform bacteria denote a group of thermotolerant coliform organisms, optional aerobic or anaerobic, which grow at 44 ± 0.5 °C and ferment lactose to produce acid and gas. Presence of faecal coliform bacteria in the natural waters may indicate the faecal contamination and degradation of the water bodies originating from diffuse sources such as urban runoff and transport from sewer overflows. Colifrom bacteria are measured with:
a. Membrane filtration and direct counting
b. Most probable number (MPN) method

Units: % change

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Surface imperviousness is characteristic of urban areas and an important environmental indicator. As surface imperviousness increases, the volume and velocity of surface runoff increases and there is a corresponding decrease in water infiltration. The impermeability of urban surfaces originates from constructing buildings, roads, parking areas, etc., with materials that are not permeable to water. When measuring water flow parameters in the field (field-saturated parameters), the measurements in the unsaturated or vadose zone (above the water table), are typically conducted using various ring infiltrometer and borehole or well permeameter methods. In the saturated zone (below the water table), water flow parameters (saturated parameters) are usually measured using auger hole methods, and at greater depths using piezometer methods.

Units: % change

Short description: Surface imperviousness is characteristic of urban areas and an important environmental indicator. As surface imperviousness increases, the volume and velocity of surface runoff increases and there is a corresponding decrease in water infiltration. The impermeability of urban surfaces originates from constructing buildings, roads, parking areas, etc., with materials that are not permeable to water. When measuring water flow parameters in the field (field-saturated parameters), the measurements in the unsaturated or vadose zone (above the water table), are typically conducted using various ring infiltrometer and borehole or well permeameter methods. In the saturated zone (below the water table), water flow parameters (saturated parameters) are usually measured using auger hole methods, and at greater depths using piezometer methods.

Units: mm/day

Short description: Evapotranspiration (ET) is a combination of two separate processes whereby water is lost from the soil surface by evaporation and from vegetation by transpiration. Evapotranspiration is measured involving specific devices and accurate measurements of various physical parameters or the soil water balance in lysimeters. In practice, ET is commonly calculated using meteorological data. Commercially-available ET monitoring stations are generally meteorological stations that calculate potential ET using monitored temperature, relative humidity, wind speed and direction, solar radiation, and precipitation data.

Units: m³/s, L/s or similar units

Short description: Rapid urbanisation and industrialisation have led to reduced vegetative cover and decreased water storage in the subsurface, as well as the concentration and accumulation of surface runoff in sewage systems due to reduced infiltration into the soil. As a result, the volume of surface runoff as well as the velocity and time to peak storm runoff and baseflow are all increased. Assessment of the effectiveness of flood management methods can be performed by different methods. For example, the assessment of runoff can be performed by in situ measurements before and after construction of a flood management structure.

Units: h

Short description: Rapid urbanisation and industrialisation have led to reduced vegetative cover and decreased water storage in the subsurface, as well as the concentration and accumulation of surface runoff in sewage systems due to reduced infiltration into the soil. As a result, the volume of surface runoff as well as the velocity and time to peak storm runoff and baseflow are all increased. Assessment of the effectiveness of flood management methods can be performed by different methods. For example, the assessment of runoff can be performed by in situ measurements before and after construction of a flood management structure.

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