Aguamilpa - El Cajon Watershed

Rainfall Runoff Study - 2008El-Cajon Watershed Rainfall Runoff Modeling

 

Team Members

Mexico Team

Contacts

Data

Weekly Progress

Feedback

WMS-HMS Tutorial

Group Presentation

Final Report

Data & Model Archive

 

 

   

Project Description

General background

Stream flow in a river is derived from the hydrological balance of its watershed. If one focuses on the hydrologic cycle of a watershed, precipitation, evapotranspiration, surface runoff, infiltration, and base flow are dominant processes that are important to study and understand if we want to use water resources effectively. This collaboration project between BYU and our Mexican counterparts, ITESO and CIATEJ, will focus on El Cajon Watershed, which contributes to the bigger Aguamilpa Watershed, located in the western part of Mexico. We believe this type of research will benefit the country in a significant way, because, due to its economical, political and social impacts, an adequate management of water resources in a country is important to its development.

El Cajon Watershed is distributed in both Jalisco and Nayarit states in Mexico. It has an approximate area of 54,198 km².  It can be divided into six sub basins, which are Arroyo Palmillas, Rio Joraviejo, Arroyo el Platanar, Arroyo Santa Fe and Rio Santo Tomas. Water from this watershed drains in Santiago River and feeds El Cajon Dam, which is the outlet point for the watershed. The El Cajon dam and reservoir are located in the state of Nayarit (21°25’41” N, 104°27’14” W), 47 km from the capital, Tepic. This reservoir helps regulate the watershed runoffs and benefits the downstream Aguamilpa Dam, because as it receives the regulated contributions of the river, it increases Aguamilpa stable generation and reduces the probabilities of flow through the spillway.

In the area of El Cajon Dam, the maximum monthly mean temperature is 32°C (May) and the minimum is 23°C (Jan); the maximum monthly mean precipitation is 242 mm (Jul) and the minimum is 0.2 mm in the month of December.

 

Scope and Objectives

Problem Definition: Analyze the amount of water that flows into El Cajón to help Mexico plan the reservoir regulation.

Scope/goal: 1. Develop Rainfall-Runoff Model for El-Cajon Watershed.

                      2. Compare modeling performance between large and small watersheds using both GSSHA and HMS.

Methodology

We are planning to analyze El Cajón watershed using HEC-HMS and GSSHA. Since, the watershed is really large, for using HEC-HMS, the watershed will be divided into six sub-watersheds. Each sub-basin will then be routed through the reaches to the El Cajón dam location. One of the tributaries will be analyzed separately that represents a smaller basin and will be analyzed independent of the entire watershed. This will give us a comparative study of the model performances for both the large and small watersheds. We will be performing long term simulation of the rainfall-runoff behavior of El Cajón watershed.

As second phase of study, we will study the same watershed with physically based GSSHA model. As GSSHA is distributed hydrologic model, it will take into account the variation in soil and other watershed parameters. We will analyze how this model behaves with both large and small watershed.

The data needed for the study are listed below:

  •  Digital Elevation Model (DEM) data for the watershed

  •  Soil type data (preferably shape files)

  •  Land use data (preferably shape files)

  •  Historical rainfall records

  •  Historical Evapotranspiration data

  •  River gauging data

  •  Topographic map of the study area

We have planned to accomplish the above mentioned objectives working in the following order.

  1. Data Collection:  As the first and basic step of our research, we have collected all of the above mentioned data sets. We got the DEM from web server and rest of the data from our Mexican Counterpart Mr. Hugo De Alba. He has been working on the same area and we are heading in the same direction with our parallel research program.

  2. Watershed Delineation:  We will use WMS 8.0 for the watershed delineation part of our study. As already outlined, the El Cajón watershed will be subdivided into six sub-basins. We will divide the sub basins based on the location of river gauging stations so that the simulated hydrograph at the intermediate locations can be compared with the observed hydrographs. But as GSSHA itself is a distributed model, we will analyze the whole watershed without dividing into smaller areas.

  3. Model Formation:  Based on the soil and land use data available, we will extract necessary hydrologic parameters. These parameters will be used to feed into the hydrologic models. Some of these parameters will be used for model calibration as well.

  4. Calibration: Both HMS and GSSHA will be calibrated for the El Cajón watershed based on the data available. Calibration will be done using Auto-calibration option of HMS and for GSSHA calibration, we will have to perform manual calibration.

  5. Mexico Visit:  We will be visiting Mexico from March 1st to March 8th. during this period, we will have time to share our findings with our Mexican counterparts. At this stage we can further our refine our model, add or deduct some part of the research from the study as per the mutual progress and objectives. We will present our findings there.

  6. Validation:  Based on the data availability, we will validate our calibrated models.

  7. Model Performance Comparison: As we have to work on the limited time frame, we have decided to put this part of our research as conditional. If we will be able to perform all the model formation, calibration and validation works within time, then we will perform this analysis too. Otherwise this part might be skipped. In this part we will analyze the accuracy in results obtained from two different models and under two different watershed sizes.

  8. Report Preparation: At the end of the semester we will summarize our findings and give it a form of a report. We will also be presenting our findings in the class and will present in the Poster presentation session of graduate seminar also.

The projected timing of all the works discussed here are depicted in the time line section of this article  later here. 

Expected Outcomes

The following are our expected outcomes:

  •  Calibrated and validated HMS model for El-Cajon watershed.

  •  Calibrated and validated HMS model for Arroyo Palmillas, one of the tributaries of El - Cajon watershed.

  •  Calibrated and validated GSSHA model for El-Cajon watershed.

  •  Calibrated and validated GSSHA model for Arroyo Palmillas , one of the tributaries of El-Cajon watershed.

  •  Model performance comparison

Projected timeline