Guide for GBNI solutions

Function	Goal	Solution	Green infrastructure	Grey infrastructure	Policy intervention	Examples
Groundwater storage	Increased water security Restoring depleted aquifers Counteract subsidence Counteract coastal saline intrusion Increased water supply	Managed aquifer recharge (MAR) Aquifer storage and recovery (ASR)	Natural infiltration Revegetation Conservation agriculture [i]	Water retention/infiltration basins Runoff harvesting In-channel mechanisms Recharge wells Riverbank filtration	MAR policies Protection of recharge zones Managing groundwater discharge Land use regulations Managing groundwater use/entitlements Groundwater markets/payments for ecosystem services (PES)	Japan United Arab Emirates India Spain Nebraska, USA Kenya
Water retention/regulation	Increased climate change resilience Increased disaster risk reduction (DRR) Increased water supply	MAR and ASR during floods/wet periods Recovery during dry periods	Floodplains Wetlands and lakes	Water retention/infiltration basins Runoff harvesting In-channel mechanisms Irrigation canals Recharge wells	Climate change adaptation DRR policies Land use regulations Managing groundwater use/entitlements	Ethiopia/Kenya India
Water quality	Improved water quality Enhanced environmental quality Counteract coastal saline intrusion	Water purification through (partial) in-situ processes MAR and ASR	Subsurface environment providing: Natural and in-situ attenuation of contaminants [ii] Carbon and nutrient regulation [iii] Riparian buffer strips	Pump-and-treat solutions Managed/enhanced in-situ soil and aquifer treatment Reactive subsurface barriers Subsurface dams Riverbank filtration Injection wells in coastal areas	(Ground)water and soil quality standards Groundwater and soil protection policies Pollution liability regulations Stormwater, wastewater and sanitation policies	The Netherlands India Germany Australia Bangladesh India
Environmental support	Increased environmental flows Protected biodiversity Increased water supply Increased aesthetic value	MAR and ASR Natural recharge and discharge protection	Protecting springs Protecting pressure of artesian aquifers Protecting natural recharge and discharge areas	Water/runoff retention/infiltration basins In-channel mechanisms Irrigation canals Recharge wells Capping freely flowing artesian wells	Reserve/ environmental flow requirements (Ground)water quality standards Recipient environmental quality standards Land use regulations Managing groundwater use/entitlements Regulation of recharge/discharge Regulation of boreholes and drilling	California, USA India Australia

[i] Conservation agriculture is based on three principles: minimal soil disturbance, permanent soil cover and crop rotations (http://www.fao.org/ag/ca/).

[ii] The United States Environmental Protection Agency (US EPA) defines natural attenuation as “a variety of physical, chemical, or biological processes that, under favorable conditions, act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in soil or groundwater. https://toxics.usgs.gov/pubs/eos-v82-n5-2001-natural/

[iii] This includes conversion, retardation, immobilization, inactivation and elimination of contaminants [5]