VLOOKUP is an Excel function to lookup and retrieve data from a specific column in table. This function is lookup a value in a table by matching on the first column. The syntax of the function as follows:
value – The value to look for in the first column of a table.
table – The table from which to retrieve a value.
col_index – The column in the table from which to retrieve a value.
range_lookup – [optional] TRUE = approximate match (default). FALSE = exact match.
It is very useful, especially in hydrology when you need to rearrange the data based on something (For example, when rearrange rainfall/discharge time series). Here some example:
1- We want to find the state for each station ID (right side of the picture) based on the list of detailed station (left side).
value = station ID ( The value to look for)
table = list of detailed station (the table from which to retrieve a value).
col_index = no of column. In here, we want to retrieve a value from the state column.
range_lookup = TRUE (approximate match)
3 – You can retrieve the value after completing the formula. Simple! You can complete the rest of the empty cell.
Hai. I want to use a web imagery from ras mapper. However, i unable to display google hybrid as the web imagery, in which ras mention the error as shown in the second image. How to solve this problem? I take projection file (.pjr) from shp file of the catchment that been build in ArcGIS. Did i using the corrected .pjr?
Try to download and use (.prj) file for UTM Zone where your project is located. You can download it from spatialreference.org. Thanks
rainfall-runoff transformation (image from alanasmith.com)
For Malaysian, we have a procedure (manual) to design flood hydrograph based on the design storm rainfall intensity, such as DID ((1976; 2010). Those manual are explained very well on the corrected procedures and methods to estimate the design flood hydrograph on the gauged and ungauged catchments.
The following procedure is recommended by DID (1976) for estimating the design storm:
the design recurrence interval is selected on the basis of the guidelines suggested by Heiler and Tan (1974).
the design storm depth for the required recurrence interval is calculated from the procedure by DID (1982). The rain depth or intensity is obtained from Intensity-Duration-Frequency curve.
The areal reduction factors recommended by DID (1982) are used to convert point rainfall to catchment mean rainfall.
The temporal pattern of the design storm is not considered.
the design storm duration is taken as that duration which gives the highest peak discharge.
Note: the design storm duration is usually adopted as that duration gives the maximum discharge. this critical duration is found by trial and error by calculating the design flood for a range of storm duration.From the experience, the duration within the catchment lag (time concentration) gives the maximum discharge.
DID (1982), Estimation of the Design Rainstorm in Peninsular Malaysia. Hydrological Procedure No. 1.
DID ( (1976). Design Flood Hydrograph Estimation for Rural Catchments in Peninsular Malaysia. Hydrological Procedure No. 11.
DID (2010). Estimation of design flood hydrograph using clark method for rural catchments in Peninsular Malaysia. Hydrological Procedure No. 27
Heiler T.D and Tan H.T (1974). Hydrological Design Return Periods, Provisional Hydrological Procedure.
Berikut adalah tutorial untuk mencari parameter untuk model Neyman-Scott, serta cara simulasi bagi mendapat data hujan (skala sejam). File sokongan dan source code untuk tutorial boleh dimuat-turn disini (Link).
PART 1: Mencari ciri-ciri hujan setiap bulan
PART 2: Mencari parameter Nyeman-Scott menggunakan ABC optimization (MATLAB code)
PART 3: Simulasi hujan skala sejam menggunakan model.
Saya ada menyediakan tutorial yang mudah untuk memasukkan data hujan dan sebagainya ke dalam HEC-DSSVue. Program ini boleh didownload dari HEC dan digunakan untuk membantu perisian HEC yang lain seperti HEC-HMS dan HEC-RAS.