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README.md

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 ## Features
 
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+This is a very basic package that contains some commonly used functions in hydrological modeling. The functions are organized into several modules, including:
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+- hydro_arithmetic: Arithmetic operations for hydrological variables
+- hydro_file: File operations for hydrological variables
+- hydro_plot: Plotting functions for hydrological variables
+- hydro_stat: Statistical functions for hydrological variables
+- hydro_time: Time series operations for hydrological variables
 
 ## Credits