PMP refers to the reference point when it comes to the maximum amount of precipitation that can be received in a specific area (Huang & Tu, 2012). In essence, it is the maximum depth of precipitation that can accorded to a specific land area considering all the geological and characteristics as well as the geography at any time period within the year.
Various methods have been used to estimate the PMP of any specific land area but data remains to be an estimation (Blume, et al., 2007). There is no single method that can take into consideration all the variables of the land. In essence, judgement is also an important factor when it comes to determining the PMP.
There are 3 PMP models that are commonly used: the use of storm models, Finding the maximum of actual storms and using PMP charts which present generalized data (Endale, et al., 2006). Nevertheless, considering that the data presented in our analysis was based on the generalized short duration method, it is important to understand that it may be based on small basins (Donker, 2001). If the area in consideration was large, it may have been based on a number of basins.
That stated, the PMP was estimated as 640mm. This represents the uniform depth over the 3 hr. rainfall period. The first analysis will be the use of temporal patterns to determine the catchment response while the second analysis pertains the routing.
The use of temporal patterns and routing
Response is based on the knowledge that the catchment response can be based on kinematic waves which can be manipulated to flow over a specified planar surface (Lee & Bang, 2002). Unlike other methods, it represents the variance of rainfall over some time period usually in consideration. Moreover, it represents analysis from different stations within the watershed. In essence, it may be used to represent the rainfall distribution and the response rainfall over a watershed.
Using the right methods in analysis is imperative in determining the amount of water that infiltrates into the ground. This is important in determining the efficiency of a land area. Suitable land areas display a higher rate of run off. As per the inflow and outflow hydrograph above, there is relatively lower rate of outflow which indicates that the storage is effective.
Blume, T., Zehe, E. & Bronstert, A., 2007. Rainfall runoff response, event-based runoff coefficients and hydrograph separation. Hydrological sciences Journal.
Donker, N. H., 2001. A simple rainfall–runoff model based on hydrological units applied to the Teba catchment (south‐east Spain). s.l.:s.n.
Endale, D. M., Fisher, D. S. & Steiner, J. L., 2006. Hydrology of a zero-order southern Piedmont watershed through 45 years of changing agricultural land use. Part 1. Monthly and seasonal rainfall–runoff relationships.. journal of Hydrology.
Huang, J. & Tu, Z., 2012. Analysis of rainfall runoff characteristics from a subtropical urban lawn catchment in South-east China. Frontiers of environmental science and engineering.
Lee, J. H. & Bang, K. W., 2002. First flush analysis of urban storm runoff. Science and the total environment, Volume 293.