MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM NATIONAL UNIVERSITY OF FORESTRY NGUYEN PHUC THO RESEARCH ON WATER RETENTION EFFICIENCY OF FOREST FOR PAYMENT FOR ENVIRONMENTAL SERVICES FOR HYDROPOWER RESERVOIRS IN VIETNAM SUMMARY OF DOCTORAL DISSERTATION Major: Silviculture Code: 9.62.02.05 HA NOI - 2020 The dissertation has been completed at: VIETNAM NATIONAL UNIVERSITY OF FORESTRY Supervisors: Assoc Prof Dr Tran Quang Bao Assoc Prof Dr Nguyen Dinh Duong Examiner 1:……………………………………………………………… Examiner 2: ……………………………………………………………… Examiner 3: ……………………………………………………………… The dissertation will be defended before the University Board of Examiners Venue: Meeting Room E, Building A3 Vietnam National University of Forestry, Xuan Mai, Chuong My, Ha Noi Time: At………… Date……… Month…… Year 2020 LIST OF PUBLICATIONS Nguyen Phuc Tho, Tran Quang Bao (2011) The potential and solutions to increase ecological economic values of natural forest in Vietnam Journal of Economic Ecology Vol 38/2011, page 111- 117 Nguyen Phuc Tho, Tran Quang Bao (2017) Evaluate the water retention efficiency of forest in hydropower reservoirs by bio-physical indicators Journal Agriculture and Rural Development, Vol 11/2017, page, 116-124 Nguyen Phuc Tho, Tran Quang Bao (2017) Determining the value of forest environmental services for hydropower reservoirs in Vietnam Journal Agriculture and Rural Development, Vol 15/2017, page 145-152 Nguyen Phuc Tho, Tran Quang Bao, Nguyen Hong Hai (2019) Flow Characteristics of Hydropower Reservoirs in Vietnam Journal Agriculture and Rural Development, Vol., 07/2019, page 130-136 TABLE OF CONTENTS Page TABLE OF CONTENTS INTRODUCTION Significance of the Study Objectives 2.1 General objective 2.2 Specific objectives The research object and scope of the study 3.1 Object of study 3.2 Scope of study New contributions of the study 4.1 The theoretical and scientific basis 4.2 The results and conclusions 4.3 The practice The general structure of the dissertation CHAPTER LITERATURE REVIEW 1.1 Some related concepts 1.2 National and international research situation CHAPTER RESEARCH CONTENTS AND METHODS 2.1 Research contents 2.1.1 Study on characteristics of basins 2.1.2 Determining water retention capacity for hydroelectric reservoirs in the dry season 2.1.3 Determining the water retention value range of forests in hydropower reservoirs 2.1.4 Proposal the amount of payment for forest environmental services for hydropower plants 2.2 Methods 2.2.1 The methods of data collection 2.2.2 Methods of data processing 14 CHAPTER RESULTS AND DISCUSSIONS 15 3.1 Characteristics of the basins 15 3.1.1 Characteristics of the observed basins 15 3.1.2 Some characteristics of forest and forestland states related to water flow in basins 16 3.2 Water retention capacity of the forest for hydropower reservoir in the dry season 16 3.2.1 Water retention capacity of the forest for hydropower reservoir in the dry season 17 3.2.2 Water retention per hectare of forest 18 3.2.3 Water retention of forest per kWh of electricity 18 3.2.4 Water retention of forest per cubic meter of water 18 3.3 The monetary value of water retention efficiency of forests 19 3.3.1 Correction coefficient 19 3.3.2 Range of water retention value of the forest 19 3.3.3 Range of water retention value per hectare of forest 19 3.3.4 Range of water retention value per kWh of electricity 20 3.3.5 Range of water retention value of forest per one cubic meter of water 20 3.4 Proposal the amount of payment for forest environmental services for hydropower plants 20 3.4.1 Principles for determining the number of payments for forest environmental services 20 3.4.2 The estimation of the range of payment for forest environmental services for hydropower plants per kWh of electricity 20 3.4.3 The estimation of payment for forest environmental services for hydro-electricity per hectare of forest 21 CHAPTER CONCLUSIONS 23 4.1 Conclusions 23 4.2 Existence and recommendations 24 INTRODUCTION Significance of the Study Payment for forest environmental services has contributed greatly to raising social awareness about the value of forest environment, benefits, rights and obligations of those who are paid and have to pay (both of payee and payer) The policy of payment for forest environmental services (PFES) has been applied effectively in life and has brought many positive aspects However, the implementation of PFES policy has not been thoroughly resolved, the determination of PFES value and level is still not scientific and not sufficient to convince PFES users as well as forest owners The scientific basis for determining the value of PFES directly affects the effectiveness of the advocacy and policy implementation process The lack of basis leads to reduction of the policy value of the forest environment So far, although there have been legal documents issued and applied in practice; there is no detail, specific and comprehensive research confirming the exact role and value of keeping the water of the forest to satisfy the parties involved in PFES, especially PFES for hydropower reservoirs From the urgent issue, the topic “Research on water retention efficiency of forest for payment for environmental services for hydropower reservoirs in Vietnam" is conducted as necessary, great scientific and practical implications." Objectives 2.1 General objective Supplementing the scientific basis for completing the policy on PFES 2.2 Specific objectives 1- Determining the water retention value of the forest in the hydropower reservoir area 2- Establishing the range of water retention value of the forest as a basis for proposing the amount of PFES The research object and scope of the study 3.1 Object of study The research object of the study is the ability of forests to retain water in some hydroelectricity plants in Vietnam 3.2 Scope of study - Spatial scope: The study space was conducted with 66 hydropower reservoir basins in Vietnam - Temporal scope: The data was collected in the basins in 2012 and 2013 - Content: The study focuses primarily on the value of forest environmental services through the role and ability to retain water in the dry season for hydropower plants New contributions of the study 4.1 The theoretical and scientific basis - Supplementing the scientific basis for the selection of methods to study the water retention capacity of forests; - Contributing to providing a scientific database of policies for payment of forest environmental services in hydroelectric lakes in Vietnam 4.2 The results and conclusions - Identify characteristics of basins; - Identify the role and value of water retention of forests in the dry season; - Establish a range of the amount of forest water retention services according to forest origin, forest types and forest status in hydropower reservoirs; - Propose the amount of PFES for some hydropower plants in Vietnam 4.3 The practice Supporting managers in planning and calculating the amount of PFES in compliance with local conditions to improve the effectiveness of forest protection and development in Vietnam The general structure of the dissertation The outline of the dissertation as following: - Along with the introduction, the main part is presented, including chapters: + Chapter 1: Literature review + Chapter 2: Research contents and Methods + Chapter 3: Results and Conclusions - References including English documents and Vietnamese documents; - 38 tables are numbered in order; and - 18 images are numbered in order CHAPTER LITERATURE REVIEW 1.1 Some related concepts The dissertation cited relevant concepts through legal documents Such concepts include (1) Forest environment; (2) Forest environmental services; (3) Payments for forest environmental services; (4) Water retention capacity of the forest 1.2 National and international research situation In this section, the dissertation has summarized all the national and international research on issues related to the study including: (1) Amount of forest value; (2) Water retention capacity of the forest (including conditions affecting water retention capacity of the forest, mechanism of them, evaporation and flow characteristics in basins); (3) Payment for forest environmental services CHAPTER RESEARCH CONTENTS AND METHODS 2.1 Research contents 2.1.1 Study on characteristics of basins 2.1.2 Determining water retention capacity for hydroelectric reservoirs in the dry season - The effect of water retention on forest per hectare; - The effect of water retention on forest per kWh; - The effect of water retention on forest per cubic meter of water; 2.1.3 Determining the water retention value range of forests in hydropower reservoirs - The water retention value range of forest per hectare; - The water retention value range of forest per kWh; - The water retention value range of forest per cubic meter of water 2.1.4 Proposal the amount of payment for forest environmental services for hydropower plants - Principles for determining the payment rates for forest environmental services; - Proposal for payment of forest environmental services for hydropower plants; - Determine the payment rates for forest environmental services for hydropower plants 2.2 Methods 2.2.1 The methods of data collection 2.2.1.1 Research methods of hydrological indicators In the world, there are three main groups of methods to study hydrological indicators in relation to influencing factors In this topic, the dissertation uses research methods on many basins that are not similar 2.2.1.2 Identify biophysical criteria To study this content, the topic has experimented with methods that have been and are being applied in practice, including Method using test yards, method using wooden stakes, method using erosion barrier, method of using erosion trap, method using hydrographic observation station and method using mathematical model with eight evaluation criteria for each method In which, there are some important criteria that are evaluated by weight factor Based on that, the study has selected the most optimal and effective method, which is the method using the hydrographic observation station with the highest total evaluation score This method is implemented as follows: Constructing hydrographic stations to investigate the flow in the output section of many basins with different characteristics, thereby analyzing the effects of vegetation cover and factors to the water output at the point of discharge of the basin (1) Information needs to collect a The general information: General information includes boundary, area, elevation, the average slope of the basin, area of forest status, precipitation transported in the basin, flow and sediment of 66 basins (including 17 basins with national observation stations) distributed in regions across the country Area and boundary of basins: The research basins have boundaries and areas that are entirely within the territory of Vietnam The boundaries of the research basins are determined by the Digital Elevation Model (DEM) with the help of ArcGIS software and verified by analyzing the distribution of contour lines on the 1: 50000 topographic map The area of the basins is determined by the map boundary and the CartesianArea function of Mapinfo software - The average elevation of the basin: the average elevation of the basin is determined by the Digital Elevation Model (DEM) with an equal distance between elevation points of 30m - The average slope of the basin: the average slope of the basin is also determined through the DEM model and the slope function of ArcGIS software follows these steps: Spatial Analysis Tools  Surface  Slope - The area of forest status in the basin: for small and medium basins where flow and sediment flow were directly investigated in 2012, 2013, this forest status map is reviewed and supplemented by using LANDSAT satellite image with a resolution of 15m Landsat satellite images are free to download at the website: https://earthexplorer.usgs.gov/ The area of the forest statuses in the basin is determined on the forest inventory map for the period of 2013 - 2016 published by the Ministry of Agriculture and Rural Development - Precipitation: Precipitation is measured by udometer in 49 basins without a national monitoring station along with the flow and sediment monitoring periods The location of the measuring station shall not exceed km from the point of measurement of flow and sediment Measurement time: at o’clock and 19 o’clock daily (a new day from 19 o’clock) - Flow, the height of water level: Concrete sluices (cylindrical and box) with the system of blocking soil and sediment to stabilize the flow Time of investigation: For temporary observation stations, the survey time is conducted once or 10 twice depending on the weather of the survey Specifically, + Investigate time on a sunny day at 7-8 o’clock, days after rain; + Investigation times: a rainy day at 7-8 o’clock and 17-18 o’clock, less than days after the rainy day The time for measurement is from 46 to 76 days during the transition period from the beginning to the middle of the rainy season The height of water level: is determined by the measure of water before and after the sluices Flow rate: measured by foam float, drifting from front to back of drain, made three times in a row for each survey point For 17 basins have national observation stations: The hydrographic survey at national hydrographic stations is conducted according to the general procedure which is twice a day at AM and PM For this content, the dissertation has monitored the flow in 49 basins and used the flow monitoring data of the Vietnam Meteorological and Hydrological Administration in 17 other basins The observed data for the national hydrographic stations are for the whole year 2007, with other stations starting from July or August and lasting from 1.5 to 2.5 months in 2012 and 2013 This is the transition period from the beginning of the rainy season to the highest rainfall period of the year The catchment areas range from a few hectares to hundreds of thousands of hectares b Methods for determining the amount of water retained by the forest during the dry season - Determine the flow volume for months in the dry season: In this study, each hydrological station is considered an outlet point to collect water from a hydroelectric reservoir The amount of water through the hydrographic monitoring station is determined by analyzing the process flow Based on the rainfall distribution by months of the year, it is possible to determine the dry season months for each place (6 consecutive months with the lowest rainfall) - Determine the total amount of additional flow due to the forest: Using empirical equations with impact factors to calculate the total amount of water for different forest cover levels will determine the total additional flow due to the influence of the forest - Determine the standard forest area: The standard forest area and the area ratio are determined according to the water holding capacity of forest statuses The standard forest area is the forest area that has been modified to retain water equivalent to the status with the highest water holding efficiency natural forest 11 - Develop empirical equations related to dry season water amount with influencing factors: The relationship between the dry season water amount and influencing factors was built through statistical analysis of data collected at 66 hydrographic stations on the total flow of the dry season, catchment area, elevation, slope, precipitation, and forest cover rate in the basin - Determine the number of cubic meters of water retained by the forest that supplies the flow during the dry season: The number of cubic meters of water retained by the forest for supply during the dry season is determined by changing the standard forest cover from to 100% in the empirical equation between these quantities and the influencing factors c Converting the value of forest environmental services in the hydroelectric area from biophysical criteria to money Using the market price method: the value of the forest water holding service is calculated by the amount of water retained by the forest for hydroelectricity in months of the dry season multiplied by the water price of the irrigation charge d Study on the method of determining the adjustment coefficients of payment for forest environmental services K Determine the coefficient K for payment of forest environmental services based on forest origin, rich and poor level, protection level by the comparative method Accordingly, the coefficient K of a forest status will be determined by the ratio of the environmental value of the forest state to the environmental value of the forest status with the best environmental efficiency The coefficient K will be determined individually according to each criterion that affects decisively on the value of forest environmental services, including forest type (protection forest, special-use forest, etc.), forest origin (plantation forest or natural forests), forest status (rich, medium or poor forests, etc.) For a specific forest plot, there will be adjustment coefficients of payment for forest environmental services: K1 by forest type, K2 by forest origin and K3 by forest status (1) Principle of determining the coefficient K The principles for determining the correction factor K are as follows + The coefficient K must change according to the environmental efficiency of the forest + The coefficient K must be easy to apply in practice + The coefficient K should support the promotion of community rights and responsibilities sharing in forest protection and development 12 + The coefficient K is determined by the comparative method + The coefficient K is determined by the index related to environmental efficiency (2) The criteria for determining the coefficient K The used criteria for determining the coefficient K are forest type and status (3) The index used to determine the coefficient K The index used to reflect the value of services is an indicator of the water retention capacity of the forest (W) e Method of determining the value of forest water storage service for hydroelectricity per ton of land, one cubic meter of water and one kWh of electricity: The value of forest water retention per cubic meter of water is defined as 25% of the unit price of electricity sold with the amount of power generated by the plant from one cubic meter of water The water retention value of forests per kWh is determined by dividing the total value of water retention service by the total electricity output of hydroelectricity generation facilities 2.2.1.3 Establish a range for the value of forest environmental services for hydropower generation facilities in the study basins The value of forest environmental services for each kWh is determined by dividing the total value of forest environmental services by the commercial power output of the plant The value of forest environmental services calculated per cubic meter of water is determined by dividing the total value of forest environmental services by the total cubic meters of water provided by the forest during the dry season for the hydroelectric plant The value of forest environmental services for a hectare of forest is determined by dividing the total amount paid for forest environmental services by the standard forest area in the basin 2.2.1.4 Determine the range of payment rates for forest environmental services for hydropower generation facilities nationwide In order to determine the framework for payment of forest environmental services to hydropower generation facilities nationwide, the empirical equation reflects the relationship of natural and socio-economic factors with the value of forest environmental services and the payment of forest environmental services are established Based on that, we define the range of payment rates for forest environmental services per hectare of standard forest and per kWh of electricity In order to develop empirical equations, the calculated data in the basins and comparative methods are applied through 13 changes in the value of water retention services of forests, changes in K coefficient, change the level of payment per hectare of forest and the level of payment per kWh of electricity according to natural and economic and social factors 2.2.2 Methods of data processing The collected data is processed by appropriate statistical software Through analysis, processing, and calculation, the thesis has implemented a number of specific steps: - Determine the standard forest area; - Converting the value of forest environmental services in the hydroelectric area from biophysical criteria to money; - Determine the adjustment coefficient for payment of forest environmental services K - Determine the value of water retention service for hydroelectricity of one hectare of a forest with the payment adjustment coefficient K; - Calculate the value of water retention service for hydropower of a hectare of a forest with the composited K factor of 1; - Determine the amount of payment for a forest plot for water retention services 14 CHAPTER RESULTS AND DISCUSSIONS 3.1 Characteristics of the basins 3.1.1 Characteristics of the observed basins 3.1.1.1 General characteristics The results showed that the characteristics of the research basins as follows: + Research basin characteristics are relatively diverse: with a basin area ranging from a few hectares to a hundred thousand hectares The height of catchment points of the basins ranges from 87 to 1081m, an average of 422m The average slope in the basin is from to 30 degrees, the average is 19 degrees + The proportion of forest area in basins has large fluctuations: The area of natural forests, planted forests as well as the forest area in general in basins fluctuates to a great extent Forest area ratio ranges from to 100%, an average of 63% 3.1.1.2 Flow rate The results show that the flow rate in the basins varies from a few m3/s to hundreds of m3/s The maximum flow rate (qmax) is to 30 times higher than the average flow rate (qtb), an average of 13 times The lowest flow rate (qmin) ranges from approximately to tens of m3/s The analysis of the characteristics of flow changes in the basins gives some conclusions: 3.1.1.3 Relationship between total flow and total rainfall The total flow is closely related to the total rainfall that precipitated into the basin On average, the total flow is about 0.82 times the total rainfall The relationship of the total flow with the total rainfall is very tight by the linear equation y = 0.7733x-5.0956 (R2 = 0.97) Thus, the total flow depends mainly on the total rainfall For 17 basins with observable data for the whole year, the ratio of the total flow to the total annual rainfall is: The average annual rainfall in these basins is 2257mm, which corresponds to 573 mm of rainfall spent on evaporation in a year, averagely a month is 47.7mm, and averagely a half of year is 286.6mm 3.1.1.4 The relationship between the total flow and the total rainfall that falls into the basin The results of the relationship analysis show that: - The average flow rate, the highest flow rate and total flow (Qdc) are closely related to the total rainfall in the basin with the correlation coefficient in the order of R2 = 0.96 and 0.92 The correlation coefficient between the 15 flow rate and the total amount of rainfall in the basin is greater than 0.85, except for the lowest flow (R2 = 0.5) - The relation of the lowest flow rate (or dry season flow) to the total rainfall is not as close as the relation between the highest flow rate and the average flow rate with the total rainfall 3.1.1.5 Relationship between flow rate and slope The relationship between the lowest flow rate and the total rainfall is always lower than its relationship with both the total rainfall and slope, the correlation coefficient R increases from 0.82 to 0.89 The lowest flow rate is closely related to the total rainfall and the average slope of the basin The larger the average slope of a basin, the higher the lowest flow rate 3.1.1.5 Rainfall and flow characteristics by months of the year The results show that in the tropical conditions of heavy rainfall in Vietnam, the total flow is directly dependent on the total rainfall Up to 97% of the total flow directly depends on the total rainfall The amount of water through the hydrological monitoring station is considered the amount of water accumulated to a hydropower reservoir where the dam is located at the hydrological station, which is determined by analyzing a chart of rainfall changes by months in a year The data show that the rainy season in different localities sooner or later, but all last on average months The rate of rainfall in the dry season compared to the total rainfall in the basins reaches from 3.2 to 25.4% Meanwhile, the ratio of dry season flow to total flow is from 13-36% 3.1.2 Some characteristics of forest and forestland states related to water flow in basins Calculation results show that for the forested state in the study area (through 177 OTC) shows: + The tree height reaches an average of 12.8m, values from 8.3 to 15.6m with the biggest fluctuations being in the state of restored and planted forests of acacia mangium (4.0 and 4.5m ) + The average canopy cover in the forest states (excluding the states without forest covers such as shrubs and upland fields) is from 26.0 to 63.4% with standard errors from 7.1 - 19.8% + Forest coverage is from 41.0 to 71.8% + The percentage of dry litter in the studied forest areas in each forest status has a value ranging from 36.0 to 78.9% 3.2 Water retention capacity of the forest for hydropower reservoir in the dry season 16 3.2.1 Water retention capacity of the forest for hydropower reservoir in the dry season 3.2.1.1 Determining the conversion coefficients that are different from standard forests 3.2.1.2 Standardized forest area in the basins 3.2.1.3 Relationship between dry season flow module and some basin characteristics The analysis results show that the total dry season flow per ha, also known as dry season flow module (Mk), is relatively closely related to the index K = ((Lm) × (Doc)0.5 × (TLRQD1)), The indicator of forest cover rate is a factor that makes up the index K Thus, the effect of the standard forest rate on the dry season flow is uniform The higher the percentage of standard forest covers, the greater the dry season flow module Among the three factors that most significantly affect the flow in the dry season of the basin, the two factors of precipitation and the average slope of the basin are little changed, and the remaining factors belong to easily changing biological characteristics that are the standard forest cover rate The empirical equation for dependency is: Mk = 0.0061 × K1 × (K2 + K3) + 344 + The efficiency of water retention of forests increases according to the forest coverage rate + The efficiency of water retention of forests increases with rainfall and the average slope of the basin The dissertation used the above empirical equations and data on area, average slope, forest cover rate, rainfall, amount of water provided by the forest during the dry season in 32 hydropower reservoirs with basin in interprovince that has identified the average annual dry season flows from one hectare of the basin in the current forested condition, the average dry season flow from one hectare of the basin in the non-forested area deviations from the total dry season water flow between the forested and non-forested watersheds in the basin and the average dry season flow from a hectare of standard forest The results show that the differences in the standard forest cover rates, the average slope in the basins and the average rainfall in the basins have made the average water retention efficiency of each hectare of forest different ranging from 1,839 to 4,565m3/ha In the North, an average of of forest holds 3,162 m3/ha of water to provide hydroelectricity in the dry season, in the Central Region is 3,235m3/ha and in the Central Highlands is 2,898m3/ha, the national average is 2,668m3/ha Water efficiency for electricity generation of hydropower plants in 17 Vietnam is determined to vary from 0.1334 to 1.4579 kWh per cubic meter If we calculate the average water efficiency for electricity generation in Vietnam by dividing the total electricity generation by the total amount of water put into the turbines of the six largest hydropower plants, the result is: H= = 0.1714 (kWh/m3) It is noticeable that the water efficiency of the plants is not the same, with one cubic meter of water generating this hydropower plant generating 10 times more electricity than other hydropower plants The water efficiency of the hydropower plant is directly proportional to the height of the water column that is fed into the turbine The equation for the efficiency of water use (H) with the height of the water column (h) is written as follows H = 0.00298 × h0.93 + 0.00141, R2=0.97 3.2.2 Water retention per hectare of forest - The value of water retention per hectare of forest in different basins is relatively clear The aggregate value of water retention per hectare of forest from 530,000 to 1,500,000 VND depending on the basin characteristics and water efficiency of a hydropower plant The close relationship of the environmental service value of a hectare of forest with the influencing factors is shown in the empirical equation with a high correlation coefficient E = -221445-7806,74 × (TLRQD2)+2093,954 × (Hcn) +22022 × Doc + 529,36 × (mua), R=0,95 3.2.3 Water retention of forest per kWh of electricity - The average water retention value of the forest per kWh of electricity also depends on many factors, especially the height of the water column to the turbine of the plant, ranging from 63 to 368 VND / kWh, an average of 214 VND / kWh electricity - The related equation for the value of forest environmental protection services in forests per kWh is: E = 266,91709 + 2,94894 × (TLRQD2) 0,56876 × (Hcn) - 11,19798 × Doc - 0,00246 × (mua), R=0,72 3.2.4 Water retention of forest per cubic meter of water The average water retention value of forest per cubic meter of water depends primarily on the height of the water column to the turbine of the plant and less on other factors The equation for efficiency of water use (H) with the height of water column (h) is written as follows: H = 0,00298 × + 0,00141; R² = 0,97 The PFES value can be determined per cubic meter of water supplied by the forest for hydropower plants in the dry season according to the following equation: Pm = 0.6528 × h + 7.79, R= 0.99 18 3.3 The monetary value of water retention efficiency of forests 3.3.1 Correction coefficient 3.3.1.1 Determine the correction coefficient From the data on the characteristics related to the water retention efficiency of forest, the dissertation has identified the correction coefficient K according to the water retention efficiency (kW) Calculation results show that, if the K correction coefficient for protection forests is 1.0, the K coefficient for special use forests is 1.0 and production forests is 0.9 3.3.1.2 Proposal of the correction coefficient Based on the analysis of the research results to determine the K coefficient, the K coefficients can be given as follows: K1 for a natural forest is 1.00 and planted forest is 0.80 K2 for a rich forest is 1.0; the medium forest is 0.95 and the poor forest is 0.90 K3 for the protection forests is 1.00; the Special-use forest is 1.00 and the Production forest is 0.9 3.3.1.3 Correction coefficient for each forest plot in each specific case For payment of forest environmental services in the areas of hydropower reservoir for forest plot, the final correction coefficient for the payment of forest environmental services K for each forest plot in the cases of using 1, or criteria are as follows: - When using the two criteria of forest origin and forest type, there will be combinations of forest characteristics to determine the K coefficient The combination of forest characteristics and the K coefficient after being rounded to 0.05 - When using the three criteria of forest origin, forest type, and forest status, there will be 12 combinations of forest characteristics to determine the K coefficient The combination of forest characteristics and K coefficient after being rounded to 0.05 3.3.2 Range of water retention value of the forest Based on the efficiency of water retention in the hydropower reservoirs, the dissertation has determined the value of the water retention service of the forest per kWh of electricity and per hectare of forest for 32 hydropower plants with water collection area in provinces or more Data show that the total water retention value per hectare of forest is VND 211,490 and per kWh of electricity is VND 47 3.3.3 Range of water retention value per hectare of forest The value of forest environmental services per hectare of forest varies widely, depending on the characteristics of the basin and the water efficiency 19 of the plant Based on the actual nationwide scope of fluctuations of the criteria, this study has determined the range of forest environmental service value per hectare in cases where the correction coefficient K is from 0.65 to 1.00; standard forest coverage rate is from 40 to 100%, rainfall is from 1,400 to 2,600mm, basin slope is from 10 to 260, height of water column into the turbine from 20 to 200m 3.3.4 Range of water retention value per kWh of electricity The data show that the value of forest environmental services per kWh of electricity ranges from about VND 35 to VND 400 / kWh 3.3.5 Range of water retention value of forest per one cubic meter of water The value of water retention service per cubic meter of water depends on the water use efficiency of the hydropower plant Using the empirical equation relating to the value of water retention service of the forest with the height of water column into the turbine, this study has built a table to look up the water retention value of the forest 3.4 Proposal the amount of payment for forest environmental services for hydropower plants 3.4.1 Principles for determining the number of payments for forest environmental services This study has taken a number of principles to determine the number of payments for forest environmental services as follows: - The number of payments for forest environmental services must be changed in accordance with the forest type, forest status, and forest formation origin - The number of payments for forest environmental services must be easily determined in practice - The number of payments for forest environmental services should apply relatively uniformly, the amount of payment for forest environment services to those with different technological levels, in places with different favorable natural conditions - The number of payments for forest environmental services may not be equal to the environmental value created by the forest - The amount of payments for forest environmental services depends on the awareness and knowledge of stakeholders and the whole society 3.4.2 The estimation of the range of payment for forest environmental services for hydropower plants per kWh of electricity Based on the amount of payment under the Decree No 156 is VND36 per kWh of electricity and the advantages of payment options given for consideration and proposal of a common amount of payment for hydropower plants is VND 50 / kWh Thus, the amount of payment for forest environmental services in the 20 1kWh electricity selling price is: equivalent to 25% of the average value of forest environmental services 3.4.3 The estimation of payment for forest environmental services for hydroelectricity per hectare of forest The study has defined a range of payment for environmental services per hectare of forest with different K coefficients It is expressed as (1) the formula for determining the amount of payment for environmental services for a hectare of standard forest, (2) the formula for determining the normative forest area to pay for an environmental service of a hydropower plant, (3) lookup table of payment amount, (4) the formula for determining amount of payment, (5) lookup table of payment for forest plot with different K coefficients (1)- the formula for determining the amount of payment Pc for environmental services for a hectare of the standard forest: Pc = I × Where: Pc is the amount of payment for environmental services per hectare of standard forest in the reservoir area I is the percentage of money used to pay directly for the forest plots after deducting the money spent on fee management, contingency fund, etc (about 0.85) n1 is the number of hydropower plants that pay for FES for the forest area, n2 is the number of water supply facilities that pay for FES for the forest area, Di is the commercial electricity output of ith hydropower plant, Ni is the commercial water output of the ith water supply facility, Sc1i is the standard forest area that the ith hydropower plant has to pay, Sc2i is the standard forest area that the ith water supply facility has to pay r is the payment for forest environmental services per kWh of electricity, 40 is the rate of payment for forest environmental services per cubic meter of water supplied by a water supply facility (2)- The formula for determining the standard forest area Sc = Where: Sc is the standard forest area that the hydropower plant has to pay for forest environmental services, n is the number of forest plots in the catchment area (basin) of the hydropower plant, Si is the area of ith plot in the water collection area of the hydropower plant, 21 K1i is the correction coefficient based on the forest origin of the ith forest plot, K2i is the correction coefficient based on the forest type of ith plot, K3i is the correction coefficient based on the forest status of the ith forest plot, (3)- a lookup table of correction coefficients of payment for forest environmental services of a forest plot Correction coefficients K1, K2, and K3 of each forest plot are determined according to their origin, status, and type of forest (4)- The formula for determining the amount of payment for environmental services for a forest plot Pli =Pc × Sci Where: Pli is the payment level for the ith forest plot, Pc is the payment for environmental services for a standard hectare of forest in the hydropower reservoir area, Sci is the standard area of the ith forest plot, Sci = Si × K1 × K2 × K3, Si is the area of the ith forest plot, (5) A lookup table of payment for environmental services for one hectare of the forest plot with different K coefficients Based on the principle of calculating the amount of payment for forest environmental services based on the correction coefficient K and the fluctuation scope of the payment amount of forest environmental services, the study has built a table of payment amount for environmental services per hectare of a forest plot with different K coefficients 22 CHAPTER CONCLUSIONS 4.1 Conclusions Within the scope of this study, dry season flow volume is an important indicator of the role of forest water retention in hydropower reservoirs It increases with the proportion of forest cover, rainfall and average slope of the basin The water retention efficiency of each hectare of forest ranges from 1,839 to 4,565 m3 / In the North, an average of of forest holds 3,162 m3 / of water to provide hydroelectricity in the dry season, in the Central Region is 3,235 m3 / and in the Central Highlands is 2,898 m3 / ha, the national average is 2,668 m3 / In the study areas, the total water retention value of a standard hectare of forest in the Northern basin is VND 860,272, the Central is VND 975,241 VND, and the Central Highlands is VND 765,638 VND The total average water retention value per kWh of electricity in the North is 162 VND / kWh, in the Central is 171 VND / kWh, in the Central Highlands is 223 VND / kWh On a national average, the water retention value per hectare of forest is 836,970 VND and per kWh of electricity is 199 VND The correction coefficient for the payment of environmental services for the forest plot in the hydropower reservoir is determined by comparing indicators reflecting the water retention value of forest types, forest status and forest origin K1 for the natural forest is 1.00 and the plantation is 0.80, K2 for the rich forest is 1.0, the medium forest is 0.95 and the poor forest is 0.90, K3 is for protection forest is 1.00, the special-use forest is 1.00, and the production forest is 0.9 Within the study basins, the water retention value per hectare of forest in the study basins ranges from 530,000 to 1,500,000 VND The water retention value of the forest per kWh of electricity ranges from 63 to 368 VND, the average value is 203 VND / kWh The average water retention value of the forest per cubic meter of water in the North is 67 VND / m3, in the Central is 124 VND / m3 and in the Central Highlands is 58 VND / m3 In the whole country, the amount of payment for forest environmental services per hectare of forest (P) ranges from 50,000 VND to 1,700,000 VND / of forest, calculated for one kWh of electricity ranging from 35 VND to 400 VND / kWh, calculated per cubic meter of water, ranging from 20 to 350 VND / m3, The range of payment for forest environmental services includes: (1) the proposed amount of payment for the hydroelectric plant is VND 50 / kWh, which is equal to 25% of the increased revenue due to forest environmental services, equal to 4% of current electricity price, (2) amount of payment per hectare of forest ranges from VND 1,084 / of forest to VND 1,701,852 / 23 of forest, the average amount is VND 897,047 / of forest 4.2 Existence and recommendations The study is not eligible for actualizing the amount of payment for forest environmental services Recommend the management agencies of the payment for forest environmental services to create conditions for applying the study results to the reality of payment for forest environmental services This study has not yet studied the K coefficient related to the difficulty level in forest protection and management Further studies need to be additionally studied for the K coefficient according to these difficult conditions 24 ... Vietnam Journal Agriculture and Rural Development, Vol 15/2017, page 145-152 Nguyen Phuc Tho, Tran Quang Bao, Nguyen Hong Hai (2019) Flow Characteristics of Hydropower Reservoirs in Vietnam Journal... in some hydroelectricity plants in Vietnam 3.2 Scope of study - Spatial scope: The study space was conducted with 66 hydropower reservoir basins in Vietnam - Temporal scope: The data was collected... hydropower plants in 17 Vietnam is determined to vary from 0.1334 to 1.4579 kWh per cubic meter If we calculate the average water efficiency for electricity generation in Vietnam by dividing the total