There is no "Global" water shortage Water is a geopolitical issue, the biggest is clean water in 3rd world and any available water in more arid regions. The nations with the biggest water issues

• Middle East: Scarcity issues
• China: Water Quality
• India: Both, availability is also a problem... small/moderate scale programs to address water issues, India leads the charge...on small village scale water acquisition, sterilization and well recharge.

Nuclear powered desalination offers the biggest grand scale changes for some nations, however technology is not applicable to poorer nations or nations whose Large scale water issues are byproduct of being in interior of continents away from ocean. Even if.... sending water hundreds or thousands of miles to water stressed regions (Often at high altitude regions) is a particularly expensive scenario. However there are some shorter term methods.

• Rainwater harvesting An inch of water over an acre of land produces 27,000 gallons of water. So 1000 square foot roof collects 623 gallons per inch of rainfall.
• Well pit recharge
• Flood based recharging pits like above
• Desalination Co-ops (Agree to cover partial cost of plant construction/operation in exchange for percentage of water)
• Harvesting agricultural runoff
• Re-forestation programs.
• microcatchment . (Landscaping features) The name Zai pits refers to small pits are dug in which seed of annual or perennial crops are planted. The pits They are beneficial for soil because they increase insect and worm activity which in turn leads to a higher water infiltration when it rains, these pits are fertilized with manure (Human or animal) which also stores water better than sandy/clay soils. This intervention is most suitable for flat or gently sloped terrains (0-5% gradient) with a precipitation quantity of 350-600 mm. Other designs like contour bunds, Negarim and other features catch water instead of letting it runoff and allow to infiltrate into the soil.

Dryer lands receive much more rain than we assume. The Netherlands, for example get's an average of 650mm (25.6 inches) of rainfall per year. Where as Xeric region Monterrey, Mexico has 680mm (26.8 inches) of rainfall. So How can the Netherlands despite having less rain, but have more fertile soils (besides a cooler climate) Be it degraded farmland or some xeric regions. Rainfall in some areas is Seasonal....in water stressed areas; water falls only at a peak of the year often a few weeks. Some regions have dry/wet seasons with six months of rain. Terrain: rain falls on slopes, hills and mountains and then flows out into streams and rivers that convey its runoff water into the sea. When areas are degraded or severely eroded, there is often a soil hardpan due to decades of compaction. The downside to no-till farming is that while it prevents soil erosion; it makes soil less permeable so only 15-25% of the water enters into the soil. The rest runs away. Pre-Industrial farmers built land terraces and planted hills, modern farming eschews that. Newly built landscaping terraces collect 3x the water to infiltrate the soil.