Hydrological Modeling: A Better Alternative to Empirical Methods for Monthly Flow Estimation in Ungauged Basins

Water resource is required for agricultural, industrial, and domestic activities and for environmental preservation. However, with the increase in population and growth of urbanization, industrialization, and commercial activities, planning and management of water resources have become a challenging task to meet various water demands globally. Information and data on streamflow hydrology are, thus, crucial for this purpose. However, availability of measured flow data in many cases is either inadequate or not available at all. When there is no gauging station available at the site of interest, various empirical methods are generally used to estimate the flow there and the best estimation is chosen. This study is focused on the estimation of monthly average flows by such methods popular in Nepal and assessment of how they compare with the results of hydrological simulation. Performance evaluation of those methods was made with a newly introduced index, Global Performance Index (GPI) utilizing six commonly used goodness-of-fit parameters viz. coefficient of determination, mean absolute error, root mean square error, percentage of volume bias, Nash Sutcliff Efficiency and Kling-Gupta Efficiency. This study showed that hydrological modeling is the best among the considered methods of flow estimation for ungauged catchments.

Study on the evaluation method of diffuse radiation models——taking 5 typical cities in China as examples

Diffuse solar radiation models play an extremely important role in solar photothermal utilization,resource assess-ment and energy consumption simulation,etc.The accuracy of these diffuse solar radiation models usually need to be evaluated by various statistical parameters.Among these statistical parameters,the Global Performance In-dex(GPI)has been extensively employed in recent years because of its comprehensiveness and wide applicability.This paper takes five cities in China as representatives of 5 typical climate regions,and 12 solar scattered radia-tion models are fitted with the meteorological data of 5 cities.Based on the comparative analysis of the existing GPI calculation methods,this paper points out that there are some defects in the existing GPI,and modifies the existing GPI based on the comprehensive consideration of statistical parameters,normalization preprocessing of statistical parameters,unified evaluation direction of parameters,weight redistribution of statistical parameters,and adjustment of extreme coefficient.12 types of new GPI are established in this paper,and the performance of diffuse solar radiation models are compared based on these GPI.The rationality of GPI corrective measures is analyzed by means of the method reasonable index(MRI).The results show that the GPI calculation method(N10)which takes five corrective measures has the best performance,and the accuracy of the existing GPI can be improved by 13.33 to 65%.