Re-conceptualizing dam design and management for enhanced water and food security

Average net primary production -is the production of plant, algae and phytoplankton, which form the base of the food chain.Drawdown zone -is the area at the edge of a body of water that is frequently exposed to the air due to changes in water level.Changes in water level can be caused by evaporation or by water usage in the case of reservoirs.Ecosystem services -are classified as provisioning, regulating, habitat and cultural services, where ¡ Provisioning services refer mainly to goods that can be directly consumed, and include food, water, raw materials, such as fiber and biofuel, and genetic, medicinal and ornamental resources.¡ Regulating services comprise regulation of climate, air quality, nutrient cycles and water flows; moderation of extreme weather events; treatment of waste -including water purification; prevention of erosion; maintenance of soil fertility; pollination; and biological controls, such as pests and diseases.¡ Habitat services are those that maintain the life cycles of species or maintain genetic diversity, through quality and quantity of suitable habitat, e.g., natural vegetation that enables the natural selection of species to maintain a diverse gene pool or which serve as a source of pollinator and pest control agents.These types of habitats benefit people primarily by maintaining stocks and flows of biodiversity, which underpin and ensure the resilience of many of the provisioning, regulating and cultural services provided by ecosystems.¡ Cultural services refer to the aesthetic, recreational and tourism, inspirational, spiritual, cognitive development and mental health services provided by ecosystems.(WLE 2014)Nutrient fluxes -sediments serve as a major carrier and storage agent for nutrients such as phosphorus, nitrogen and potassium (Baran et al. 2015).Fluxes of organisms, detritus, nutrients and other materials into reservoirs strongly affect primary productivity: denitrification, burial in sediments and nutrient turnover mean that reservoirs act as nutrient sinks, blocking the flow of nutrients downstream (McCartney et al. 2016).Recession agriculture -flood recession agriculture uses the residual moisture of seasonally flooded lands when the floods recede.This may be practiced on the banks of rivers or seasonal lakes.