Depression Storage 6m6r6l

DEPRESSION STORAGE Group 9 Bautista, Mary Christine

Bioncio, El John Cabahug, Jobel Hyles Gabayan, Lorence

WHAT IS DEPRESSION STORAGE? 

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Water retained in puddles, ditches, and other depressions in the surface of the ground. The quantity of storm water that is lost as a result of minor surface depressions in the ground. When water temporarily accumulates in a low point with no possibility for escape as runoff The volume, in inches (mm), that must be filled prior to the occurrence of run off.

DETENTION STORAGE  When

the precipitation occurs for a longer duration and at a rate greater than the rate of infiltration some water is collected on the surface of the earth up to a certain depth. On attaining a certain depth, the action of gravity makes this water flow. Before it starts flowing, the water stored on the surface of earth is called detention storage.

HYDROLOGICAL CYCLE

IMPERVIOUS DEPRESSION STORAGE 

Water stored as depression storage on impervious areas is depleted by evaporation.

PERVIOUS 

DEPRESSION STORAGE

Water stored as depression storage is subject to both infiltration and evaporation.

IMPORTANCE OF DEPRESSION STORAGE Depression storage may be treated as a calibration parameter, particularly to adjust runoff volumes.  Depression storage is a type of hydrologic abstraction on the modeling of precipitationrunoff relationship  Depression storage may be of considerable magnitude and may play an important role in hydrologic analysis and flood control. 

FLOOD CONTROL

VOLUME OF WATER STORED

VOLUME OF WATER STORED 

The volume of water in depression storage at any time during a precipitation event can be approximated as

V is the volume of water in depression storage. Sd is the maximum storage capacity of the depression.

Pe is the rainfall excess k is a constant equal to 1/Sd.

FACTORS AFFECTING DEPRESSION STORAGE 1. Landform

FACTORS AFFECTING DEPRESSION STORAGE 2. Soil Characteristics

FACTORS AFFECTING DEPRESSION STORAGE 3. Topography

FACTORS AFFECTING DEPRESSION STORAGE 4. Land use

FACTORS AFFECTING DEPRESSION STORAGE 5. Antecedent rainfall index- A weighted summation of daily precipitation amounts, used as an index of soil moisture.

Retention - storage held for a long period of time and depleted by evaporation.  Detention - short-term storage depleted by flow away from the storage location.  Depression storage may be of considerable magnitude and may play an important role in hydrologic analysis. Stock ponds, terraces, and contour farming all tend to moderate flood by increasing depression storage. 

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If the soil surface has a low infiltration capacity and low hydraulic conductivity, and if the topography allows for surface storage, then water may be stored at the surface in small pools or depressions. These water-filled depressions, called vernal pools, are often seasonal features that form because of perched water tables.