Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author. WATER ACCOUNTING IN THE OROUA RIVER CATCHMENT A thesis submitted in partial fulfilment of the requirements for the degree of Master in Applied Science in Agricultural Engineering at Massey University, Palmerston North NEW ZEALAND SANTIAGO T. RECILE 1999 ii ABSTRACT With growing population and limited water resources, there is an increasing need worldwide for better management of water resources. This is especially true when all-or nearly all-water resources are allocated to various uses. Effective strategies for obtaining more productivity while maintaining or improving the environment must be formulated. This can be achieved only after the water quantity, quality and uses have been understood and evaluated . One tool to analyse the situation in order to gain a deeper understanding and possibly identify opportunities for better water management is the recently­ proposed methodology of water accounting, which considers components of the water balance and classifies them according to uses and productivity of these uses. Identified changes in quantity and quality of water can provide important clues on increasing water productivity. The water accounting methodology was tried in the Oroua River Catchment to evaluate its use as a way of assessing water availability, and to identify opportunities for water savings in the catchment. The use of the methodology in a basin-wide water assessment was not successful due to insufficient rainfall data-especially at the State Forest Park where most of the streamflow (approximately 80%) comes from during low flows. In addition, the monthly climatic water balance model used failed to produce a reliable estimate of streamflow. The volume of estimated streamflow was greatly underestimated as compared to the actual recorded streamflow. Streamflow water accounting was able to assess the water availability in the lower portion of the Oroua River for the indicators gave a clear picture of the existing state of the river during the summer months. Water depletions from instream uses, which include waste assimilation, environmental maintenance, and free-water evaporation, comprised the largest part of the total streamflow depletions in the lower Oroua River. In some instances, combined depletion from waste assimilation and free­ water evaporation was more than 3 times the available water. Depletions from offstream uses, including municipal and industrial, and irrigation abstractions iii comprised only a small portion of the total streamflow depletion. However, one limitation of the approach is that it did not account for the other return flows from irrigation and M&I diversions. Despite the limitations of the study, the use of the indicators helped in understanding the situation since the Depleted Fraction (DFavailabie) indicator clearly showed how much further abstraction is allowed, and the use of the Process Fraction (PFdepleted) readily shows an opportunity for better use of water. It is recommended that the pollution effect also be included in the original water accounting methodology of Molden (1997). The pollution effect of different contaminants could be quantified by their dilution factor i.e., the physical amount of water lost to pollution from the discharge of effluents is measured by the amount of upstream water which would be required to dilute it back down to the maximum allowed concentration of pollutants. iv ACKNOWLEDGMENTS I would like to thank the following-who were involved in the completion of my study: Firstly, my supervisor Professor Gavin Wall-for his invaluable advice, patience, and guidance in the conduct of this study. My special thanks go to the following staff of the Manawatu-Wanganui Regional Council; Ms Marianne Watson, Mr. Harold Barnett and Mr. John Phillips - for their valuable help in providing the necessary information on the Oroua River catchment, and allowing the use of their maps. I wish to thank also Mr. Kevin McGill of NIWA for providing the rainfall and evaporation data. The Filipino community-especially Fr. Raymund Soriano, the Carambas Family, Baker family, Mata Family and the Filipino NZODA scholars who, in one way or another, made our stay in New Zealand comfortable. My wife-for her moral support, prayers and patience in caring for our children during my studies; and to my mother-for her unending prayer for my success. My fellow Agricultural Engineering postgraduate students-for their encouragement and camaraderie. Finally, I would like to thank our president, Dr. Marcelino T. Delson, for his encouragement and willingness to let me further my education, and the New Zealand Government through the Overseas Development Assistance (NZODA) programme-for the Postgraduate Scholarship Award, which gave me the opportunity to pursue my postgraduate study. v TABLE OF CONTENTS ABSTRACT ........................................................................................ ii ACKNOWLEDGMENTS ....................................................................... iv TABLE OF CONTENTS ........................................................................ v LIST OF TABLES .............................................................................. vii LIST OF FIGURES ............................................................................. vii CHAPTER I. INTRODUCTION ............................................................... 1 1.1 The Glob al Scene .......... ... ... .. .... ........ ... .... ..... .. .. ....... .... ..... ..... ..... .... 1 1.2 New Zealand Situation .................... . ............................ ............... ...... 3 1.3 Problem statement. ...... ................ .... . ..... .. ......... .... ...... ............... ...... 4 1.4 Objectives of the Study ............................. ....................... ................. 5 CHAPTER II. REVIEW OF LITERATURE ................................................ 6 2.1 Introduction .......... .... ............................................ . .................... ... .. 6 2.2Classes of Water Use .. .. .......... ......................................................... 7 2.3 Efficiency of Water Resource Systems ................................................ 9 2.3.1 Water Use Efficiency .................................................................. 9 2.3.2 Classical vs Effective Efficiency ............ ... .......................... .. ... ..... 10 2.3.3 Basin-Wide Impacts of Water Efficiency ............... . .......... ....... ....... 11 2.3.4 'Wet" and "Dry" Water Savings ...... .............................................. 13 2.4 Water Resource Assessment Methodologies ....................................... 13 2.4.1 Water Balance Approach ............................................................ 14 2.4.1.1 Methods of Computation of the Main Water Balance Components.16 2.4.1.2 Water Balance Modelling ....................................................... 20 2.4.1.3 Examples of Water Balance Components Estimation .................. 24 2.4.2 Water Accounting Approach ................................................. ...... 26 2.4.2.1 Water Accounting Definitions ............................................. .... 26 2.4.2.2 Performance Indicators ............. .................... .. .. ... ..... ............ 29 2.4.2.3 Levels of Analysis ........................ .... ... .. ................. . ............. 31 2.4.2.4 Accounting Components at Use, Service, and Basin Levels ......... 32 vi 2.4.2.4.1 Field Level. ........................... .................................. ...... 32 2.4.2.4.2 Irrigation Service Level ............................................. ....... 32 2.4.2.4.3 Basin and Subbasin Levels .............................................. 33 2.5 Water Quality ........................................................... .................... 35 2.5.1 Water Quality Indicators ............................................................ 35 2.5.1.1 New Zealand Water Quality Standards .................................... 36 2.6 Conclusions ................................................................................. 37 CHAPTER Ill. THE OROUA CATCHMENT ............................................. 39 3.1 Introduction ....... ........................ ...................................... ............. 39 3.2 Catchment Description .... .. .... ................................................... ...... 39 3.3 Values Associated with the Catchment ............................................. .41 3.4 Groundwater ............ .... ....... ....... ........... . ....................................... 43 3.5 Surface Water Demands ......................... .... ................................... .43 3.6 Issues ............................ .......................... .............................. ..... 44 3.6.1 Adverse effects on river and stream environments caused by low flows in rivers during summer dry periods ............................ ......... .44 3.6.2 Unacceptable water quality in the Oroua River downstream of Feilding at times of low flow .............................. .. ............. .. .... .44 3.6.3 Management of competing demands for surface water resources ..... .45 CHAPTER IV. METHODOLOGY ................................................ .......... 46 4.1 Introduction . .................. .................. . .. .... .... ....... ....... ... ............ . ..... 46 4.4 Calculation of the Different Water Accounting Components .................... .47 CHAPTER V. BASIN-WIDE WATER ACCOUNTING ................................ 53 5.1 Introduction ................................................................................... 53 5.2 Results ........................................................................................ 53 5.2.1 Water Balance Components ....................................................... 53 5.2.1.1 Precipitation ............................................ . ............ ........ . ..... 53 5.2.1.2 Evaporation and Evapotranspiration .......... .............................. 55 5.2.1.3 Municipal and Industrial Use .................................................. 55 5.2.1.4 Water Rendered Unusable Due to Degradation of Quality ............ 57 5.2.1.5 Irrigation Abstractior;i .................................................. .......... 58 vii 5.2.2 Monthly Climatic Water Budget ................................................... 59 5.2.3 Water Accounting .. ....... .................... . .......... ............ ........... ...... 60 5.3 Discussion ................................................................................... 64 5.4 Conclusion .......................................... .. ....................................... 66 CHAPTER VI. STREAMFLOW WATER ACCOUNTING ........................... 68 6.1 Introduction .......................... .......... .. ..... ....... . ........................ ... ... . 68 6.2 Results .................. .. .................................................. ........ .......... 70 6.2.1 Total Depletion-DFavailable · ....... .. ............................................... 70 6.2.2 Process Depletion ............. ..... .. ......................... ... ..... .. .......... .. .. 71 6.3 Discussion ............. .. ... ......... ....... ............. .. ..... ............................. 75 6.3.1 Water Availability in the Lower Oroua River .................................... 75 6.3.2 Potential Water Savings ............................................................. 78 6.3.3 Suitability of the Water Accounting Methodology ....... ...................... 79 6.4 Conclusion ..... .. ..... ... ... ... ... ..... ... .. ......... .................................. ...... 81 CHAPTER VII. ANALYSIS WITHOUT THE FEILDING SEWAGE DISCHARGE ................. . ............................................. 82 7.1 Introduction .................................................................................. 82 7.2 Results ... ................. . .. .... ................................ .... ... .... .................. 82 7.3 Discussion ... ............................ ......... .. ... ................. .. ....... ............ 86 7.4 Conclusion ............. ......... .............. . ......................................... . .... 87 CHAPTER VIII. CONCLUSION AND RECOMMENDATIONS ...................... 88 8.1 Conclusions .................................................... ... ..... .......... .. ....... .. 88 8.2 Recommendations ... ...................................................................... 91 8.2.1 For the Future Use of the Water Accounting Methodology ................ 91 8.2.2 For the Management of the Oroua River ....................................... 91 APPENDICES ................................................................................... 92 Appendix 1. Hydrographs Showing the Oroua River Streamflow at Almadale From November 1997 to March 1998 (Source: MWRC) ............ . 92 Appendix 2. Daily Kiwitea Stream Streamflow at Spur Road From April 1997 To March 1998 (Source: MWRC) .................... ..... ................. 98 viii Appendix 3. Available Soil Water Capacity ............................................... 99 Appendix 4. Monthly Climatic Water Balance .................................... ...... 100 BIBLIOGRAPHY .............................................................................. 101 ix LIST OF TABLES TABLE 2.1 Water accounting components at field, service, and basin level (Source: Molden, 1997) ..... ..... ................... .... ......... ........................ 34 2.3 Manawatu-Wanganui Region requirements for discharges to water (Source: Forsyth , 1996) ..... ...................... ...... ...... ... ....................... 37 5.1 Monthly Precipitation in the Oroua River Catchment .................... ..... . ... 54 5.2 Total monthly evaporation and evapotranspiration ................................ 55 5.3 Municipal and Industrial abstraction in the Oroua River Catchment .. .. ..... . 56 5.4 Depleted water due to quality degradation ......... ................................. 58 5.5 Irrigation abstractions ........... ..... ...... ..... ... ............. ... ...... ....... ....... ... 59 5.6 Water accounts of the Oroua River Basin: April 1997 to March 1998 ........ 62 x LIST OF FIGURES FIGURE 2.1 Water accounting (Source: Molden, 1997) .............. ... ......................... 28 3.1 A map of the Oroua River Catchment (Source: MWRC) ............. ... .. ...... .40 6.1 Water depletions for the month of April ..................................... .. ....... 72 6.2 Water depletions for the month of November ...................................... 72 6.3 Water depletions for the month of December ................... ................... 73 6.4 Water depletions for the month of January .......................................... 73 6.5 Water depletions for the month of February ........ .. .... .. ... .. ... .... ... ....... .. 74 6.6 Water depletions for the month of March ............................................ 74 7.1 Streamflow depletion for the month of January without the Feilding sewage discharge ...... .. ................. ....... . ..................... .................. 83 7.2 Streamflow depletion for the month of February without the Feilding sewage discharge ............................ .. ............................ ... ... .. ...... 84 7 .3 Streamflow depletion for the month of March without the Feilding sewage discharge ....... ..... ................................................... ...... .... 85