GEOGRAPHY & CARTOGRAPHY CALCULATOR
Probabilityhydrological Drought
A precise tool.
What is the Probabilityhydrological Drought & How does it work?
Hydrological drought occurs when river discharge falls below a critical threshold for an extended period, affecting water supply, ecosystems, and agriculture.
Statistical approaches estimate the likelihood of such lowβflow events by comparing observed or projected discharges to the longβterm mean and variability of the basinβs runoff.
Assuming runoff follows a normal distribution, the probability that discharge Q is less than a threshold Q_{thr} can be expressed with the standard normal cumulative distribution function.
P = \Phi\left(\frac{Q_{thr} – \mu_Q}{\sigma_Q}\right)
P = probability of hydrological drought; Q_{thr} = threshold discharge; \mu_Q = mean annual runoff; \sigma_Q = standard deviation of runoff
Parameters
Result
β
Frequently Asked Questions
What is hydrological drought?
Hydrological drought occurs when river discharge falls below a critical threshold for an extended period, affecting water supply, ecosystems, and agriculture.
How does the calculator estimate the probability of low-flow events?
The calculator estimates the likelihood of low-flow events by comparing observed or projected discharges to the long-term mean and variability of the basin's runoff, assuming a normal distribution.
What is Q_{thr} in the context of this calculator?
Q_{thr} represents the threshold discharge below which hydrological drought is defined.
How does the standard normal cumulative distribution function (CDF) relate to this calculation?
The CDF is used to determine the probability that the discharge Q will be less than the threshold Q_{thr} by converting the discharge data into a standardized form based on its mean and standard deviation.
Can this calculator be used for any river basin?
Yes, as long as you have historical runoff data for the specific river basin, you can use this calculator to estimate the probability of hydrological drought.
What are the implications of a high probability of hydrological drought?
A high probability indicates an increased risk to water supply, potential impacts on ecosystems, and challenges for agriculture in the affected area.
How often should I update the discharge data for accurate results?
It is recommended to update the discharge data annually or as new data becomes available to ensure the accuracy of the drought probability estimates.
Results are for informational purposes only and do not constitute professional advice.