The rainy season in Zambia is from November through February and into March. Food crops are grown during this time that sustain the country for the next eight months of relatively dry weather. Declining rainfall patterns threaten not only crop production but water availability throughout the country. A recent article from The Guardian reveals that Lake Kariba, the world’s largest artificial lake, has dropped by six meters in the past three years. The Zambezi River, a key source of water for the region and the source of the stunning Victoria Falls waterfall, is at its lowest levels in 25 years. Climate change is threatening not only the water supply but the region’s biggest tourist attraction which could have lasting economic implications. Edgar Lungu, Zambia’s President, has called this trend of declining rainfall “a stark reminder of what climate change is doing to our environment” (The Guardian). aWhere’s 14 years of observed data show how these trends are occurring across the country and in specific locations (latitude, longitude). The map below is the change in the average precipitation during the rainy season of November-February for the period of 2006-2009 compared to 2016-2019. The chart narrows in on trends in a specific locations to highlight the declining rainfall pattern.
Analytics: Understanding Seasonal Variability with CV & P/PET
Weather variability due to climate change causes significant disruptions to food security, water availability, and the economy as it brings increased risk to agriculture and adjacent sectors. aWhere analysts highlight coefficient of variation (CV) to describe the extent of weather variability in specific locations. The CV is shown as a percent and as a general rule, any location with a CV of greater than 20% is considered highly variable. By understanding variability, officials can make data-driven decisions to drive new investments in irrigation infrastructure. The map below shows the CV for the month of January from 2006-2020 for Precipitation over Potential Evapotranspiration (P/PET).
P/PET is a powerful index for understanding the conditions conducive for crop production. As Precipitation (P) drops below PET (the evaporative demand of the environment), the result is dry conditions and plants start to wilt. The threshold for maize is 0.8, when P/PET is less than 0.8, maize is likely to fail. Water stress becomes acute as the P/PET ratio drops below 0.7 and below 0.6 the ecology shifts to grassland and then below 0.4 is when desert conditions prevail.
Implications and Recommendations
As erratic climate events become the norm, early warning systems must be strengthened to sufficiently warn communities of impending drought. aWhere’s daily-updated data provides the historical observed data needed to make data-driven decisions as well as the current conditions to provide relevant information to farmers and officials on the state of how weather is impacting crop production and water supply. With accurate weather data, Zambia builds resilience to weather variability and adapts to climate change.
aWhere’s weather data and models help service providers, industry and farmer producer organizations and government agencies in Zambia and around the world adapt to weather variability and deliver economic resilience to climate change in agriculture, energy, health, trade (domestic and international) and infrastructure.