Rainfall, Runoff and Soil Degradation in the Hindu Kush-Himalayas - a Case Study in Hilkot Watershed Pakistan
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Rainfall, Runoff and Soil Degradation in the Hindu Kush-Himalayas - A Case Study in Hilkot Watershed Pakistan by Suhail Zokaib A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in The College of Graduate Studies (Civil Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Okanagan Campus) June, 2011 © Suhail Zokaib, 2011 i Abstract Surface runoff and sediment transport are often considered as the two most important hydrological parameters in water resources engineering. Surface soil erosion from most of the areas is a serious threat to sustainable agriculture and sediment accumulation in reservoirs. An extensive runoff and soil erosion study was conducted in Hilkot watershed, Pakistan. The watershed consists of four major land uses including degraded, forests, agricultural, and pasture lands. The main objective of this dissertation was to provide a better understanding of the hydrologic and land use behavior of the watershed. Moreover, the goals were: 1) to calculate and compare annual rainfall, runoff and soil losses with their seasonal distribution from different land uses; 2) to establish rainfall, runoff and soil loss relationships; and 3) to develop a calibrated mathematical model for runoff and soil loss estimation. Overall, the results obtained from this research demonstrated that the Hilkot watershed falls in the monsoon region with about 38% rainfall occurred in the monsoon period (July to September). The average annual rainfall found in the study area was 1160 mm. In all the erosion plots, almost 50% of the runoff and soil loss occurred during the monsoon period. The mean maximum runoff was from the degraded plot (674 m3/ha/y), while the minimum was observed at the pasture plot (310 m3/ha/y). The average runoffs on other land uses were 529 and 460 m3/ha/y from the forest and agriculture plots, respectively. The average maximum soil loss was recorded from the degraded plot (6.5 t/ha/y) and the average minimum (1.8 t/ha/y) was on the pasture plot. Similarly, the average soil losses were 3.3 and 3.4 t/ha/y measured from the forest and agricultural plots, respectively. Polynomial regression analyses were developed for predicting rainfall, runoff and soil loss relationships and showed a reasonable correlation among the parameters. A mathematical model was also developed and calibrated with field data (using a genetic algorithm approach) to estimate the total runoff and soil loss for various land uses. The model reproduced the measured field data reasonably well and it indicated the highest and lowest runoff and soil loss for degraded and pasture lands, respectively. ii Preface This dissertation was conducted by analyzing a seven-year data set for the Hilkot watershed, Pakistan. The required data were collected for the People and Resource Dynamics Project (PARDYP) in a catchment of Terbala Dam from 1999 to 2005. I was involved with PARDYP as a hydrologist and was responsible for monitoring the network and field data collection. All data were analyzed on monthly and annual basis and a numerical model was developed and calibrated with field data at the University of British Columbia. Three papers were submitted for publication in different journals. Chapter 4 is based on submitted journal paper for publication. Zokaib, S. and Naser, B. 2010. Impacts of Land Use on Runoff and Soil Degradation in Hilkot Watershed in Pakistan. Submitted for publication in the International Journal of Sediment Research. I was involved in data collection, data analysis and paper writing. Dr. Bahman Naser was involved in editing. Chapter 5 is based paper submitted to journal for publication. Zokaib, S. and Naser, B. 2011. A Study on Rainfall, Runoff, and Soil Loss Relationships at Different Land Uses – A Case Study in Hilkot Watershed in Pakistan. Submitted to the Journal of Hydrological Research. I was involved in data collection, data analysis and paper writing. Dr. Bahman Naser was involved in editing Chapter 6 has also been submitted to the Journal of Hydrology. Zokaib, S. and Naser, B. 2011. A New Approach on Modeling Soil Erosion and Surface Runoff in a Watershed. Submitted to the Journal of Hydrology. I was involved in development of mathematical model and model calibration with field data. Dr. Bahman Naser was involved in editing. iii Table of Contents Abstract ........................................................................................................................................................ ii Preface ......................................................................................................................................................... iii Table of Contents ........................................................................................................................................ iv List of Figures ............................................................................................................................................ vii List of Tables ............................................................................................................................................... ix Acronyms and Abbreviations ........................................................................................................................x Mathematical Notations............................................................................................................................... xi Acknowledgements .................................................................................................................................... xii Chapter 1 : Introduction...............................................................................................................................1 1.1 Thesis Objectives ................................................................................................................................4 1.2 Thesis Organization .............................................................................................................................5 Chapter 2 : Research Area and Methodology ...............................................................................................8 2.1 Research Area – Hilkot Watershed .....................................................................................................8 2.2 Operational Background of the Study .................................................................................................8 2.3 Hilkot Watershed – Base Line Information .......................................................................................10 2.3.1 Population ...................................................................................................................................10 2.3.2 Land Use .....................................................................................................................................11 2.3.3 Local Climate and Seasons .........................................................................................................12 2.4 Field Measurement and Data Collection ...........................................................................................13 2.4.1 Measurement Network ...............................................................................................................13 2.4.2 Data Collection –Nested Approach ............................................................................................14 2.4.3 Erosion Plot Network .................................................................................................................15 2.4.4 Hydro Station Flow Measurements ............................................................................................16 Chapter 3 : Literature Review ....................................................................................................................20 3.1 Water Quantity/Water Scarcity .........................................................................................................20 3.2 Runoff and Soil Erosion in Hindu Kush Himalaya ...........................................................................22 3.3 Land Use and Vegetative Cover ........................................................................................................23 3.4 Sediment Budgeting ..........................................................................................................................26 3.5 Runoff and Soil Loss Modeling ........................................................................................................27 3.6 Stream Flow ......................................................................................................................................29 Chapter 4 : Impacts of Land Uses on Runoff and Soil Degradation ..........................................................31 4.1 Results and Discussion ......................................................................................................................32 4.1.1 Annual and Seasonal Distribution of Rainfall ............................................................................32 4.1.2 Annual and Seasonal Distributions of Runoff ............................................................................33 iv 4.1.3 Annual and Seasonal Distributions of Soil Loss ........................................................................35 4.1.4 Impact of Land Use on Sediment Yield .....................................................................................38 4.2 Summary ...........................................................................................................................................39