Digging Deeper Into Drought: The Palmer Hydrological Drought Index (PHDI) Explained
When people think about drought, they tend to think about the weather patterns that lead to it. But what about the long-term hydrological effects of drought? The Palmer Hydrological Drought Index (PHDI) was developed to measure both the duration and intensity of these hydrological impacts. Let's take a closer look at this index and how it works.
What Is the PHDI?
The PHDI is a long-term drought index that measures the hydrological impacts of drought, such as reservoir levels, groundwater levels, etc. It was developed in response to the operational Palmer Drought Index (PDI), which attempts to measure only the duration and intensity of long-term drought-inducing circulation patterns. The PDI can respond quickly when weather patterns change from a long-term drought pattern to a wet pattern, while the PHDI responds more slowly due to its focus on hydrological impacts.
How Does It Work?
The PHDI takes into account climate variables such as temperature, evaporation, precipitation, soil moisture, and runoff. These variables are collected over an extended period of time in order to determine whether an area is currently in a prolonged dry spell or if conditions are beginning to return back to normal. In addition, information from past years is taken into consideration when determining current conditions. This helps give scientists a more accurate picture of current conditions as well as what areas might be headed for a potential drought in the future.
Using Climatological Data To Track Impacts Of Drought
In order to track changes in hydrologic impacts due to climate variability, climatological data must be collected over an extended period of time and analyzed through rigorous statistical techniques. By combining this data with other sources such as satellite imagery and ground observations researchers are able to better understand how short-term weather events impact longer-term trends such as water availability or reservoir levels. This information can then be used by decision-makers in order to prepare for future droughts or plan for increased water resource needs during times of prolonged dry spells.
Measuring the long-term hydrological impacts of drought is important for predicting future droughts and planning accordingly for increased water resource needs during those times. The Palmer Hydrological Drought Index (PHDI) is one way we can measure those effects over time using climatological data combined with other sources such as satellite imagery and ground observations. Although it takes longer than other methods like the operational PDI, understanding how short-term weather events affect longer-term trends is essential for preparing our communities for potential droughts down the line.