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Soil: Organic Matter and Available Water Capacity
Published in Yeqiao Wang, Landscape and Land Capacity, 2020
Available water capacity (AWC) is defined as the amount of water (cm3 water/100 cm3 soil) retained in the soil between “field capacity” (FC) and the “permanent wilting point” (PWP).[1] FC and PWP are defined as the volumetric fraction of water in the soil at soil water potentials of 10 to 33 kPa and 1500 kPa, respectively. One of the paradigms of soil science is that AWC is positively related to soil organic matter (SOM) because SOM raises FC more than PWP[2–4] (Figure 33.1). SOM enhances soil water retention because of its hydrophilic nature and its positive influence on soil structure.[5,6] Increasing SOM increases soil aggregate formation and aggregate stability[7] (Figure 33.2), thereby increasing porosity in the range of pore sizes that retain plant-available water and enhancing infiltration and water retention throughout the rooting zone. When SOM decreases, soil aggregation and aggregate stability decrease and bulk density increases.[8] These changes in physical properties result in lower infiltration rates and higher susceptibility to erosion.[9,10] This entry reviews the literature on the sensitivity of AWC to soil organic carbon (SOC) and discusses the environmental implications of changes in SOM and AWC. This entry supersedes and updates a 2003 review[11] with a description of the recent literature on the sensitivity of AWC to SOM and discusses the environmental implications of changes in SOM and AWC.
Floodwater Harvesting
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Nasir Ahmad Rather, Shahid Ul Islam, Mir Bintul Huda, Saeid Eslamian
The water-holding capacity of soils is an important property that determines their water harvesting potential. Not only the holding capacity but also the level or ease with which the soil can release it are important. Water holding capacity is measured as the available water capacity (AWC); AWC along with the soil depth is very vital for adopting the suitable water harvesting technique and then utilization of the stored water for plant growth.
Hydrological simulation using the SWAT model: the case of Kalamas River catchment
Published in Journal of Applied Water Engineering and Research, 2018
The available water capacity of the soil layer (SOL_AWC) is the amount of water available to plants. It is defined as the difference of the water being present at the specific layer’s permanent wilting point (the water content retained in soil at −15 bar) from that present at its field capacity (the water content retained in soil at −0.33 bar) (Neitsch et al. 2002). According to Jah (2011), the parameter is inversely related to the water balance components (high values of SOL_AWC indicate that the soil has the capacity to retain its moisture, reducing the amount of water available for surface runoff). Its default values were reduced by 0.04 for all soil types, causing an increase in the initial surface runoff.
Impact of irrigation on the water level of Lake Maybar, Northeast Ethiopia
Published in International Journal of River Basin Management, 2019
Mezgebu Mewded Afessa, Binyam Alemu Yosef
The actual storage of soil moisture (STOR) for each month was calculated as:where AWC is the moisture storage capacity, also known as available water capacity of the soil, which is based on the land use, soil texture and rooting depth as suggested by Thornthwaite and Mather (1955, 1957).