Evaluating runoff generation and water quality at a small forested catchment study case luot mountain at vfu in xuan mai town, hanoi capital, vietnam

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM FORESTRY UNIVERSITY STUDENT THESIS Evaluating runoff generation and water quality at a small forested catchment Case study: Luot mountain at VFU in Xuan Mai town, Hanoi capital, Vietnam Major: Advanced Curriculum in Natural Resources Management Code: D850101 Faculty: Forest Resources and Environmental Management Student: Vu Duong Ly Student ID:0954011529 Class: K55 Natural Resources Management Course: 2010 – 2014 Advanced Education Program Developed in Collaboration with Colorado State University, USA Supervisor: Dr Bui Xuan Dung Hanoi, November 2014 ACKNOWLEDGEMENT I would like to express my sincere gratitude to Dr Dung and Prof: Lee Mac Donald providing continuous encouragement and enthusiastic support during the research work in I greatly appreciated the help provided for by the weather station and laboratory work at Vietnam Forestry University, and would especially like to thank Ms Diem, Mr Le who helped me directly TABLE CONTENT ABSTRACT I INTRODUCTION II OVERVIEW OF THE PREVIOUS RESEARCH ISSUES 2.1 Overview 2.2 Limitation of the previous studies III OBJECTIVE, SCOPE, CONTENT OF THE STUDY 3.1 Objective 3.2 Scope 3.3 Contents Error! Bookmark not defined IV STUDY SITE AND METHOD 4.1 Study site 4.2 Method 4.2.1 Rainfall monitoring 4.2.2 Catchment runoff monitoring 4.2.3 Observating water quality of catchment runoff V RESULT AND DISCUSSION 13 5.1 Characteristic of runoff generation 13 5.2 Runoff component 16 5.3 Water quality and characteristic of catchment 19 VI CONCLUSION 24 REFERENCES 25 LIST OF TABLE Table 1: Climate- Hydrology indicator at Xuan Mai (Ba Vi weather station) Table 2: Physical and chemical materials Table 3: Parameters index 23 LIST OF FIGURES Figure 1.Location of study site and rainfall, runoff monitoring Figure Runoff generation in forested headwater catchment over time 13 Figure 3.Characteristic of (a) Rainfall storm;(b) storm runoff;(c)Runoff coefficient in over storm event 14 Figure 4: The relationship between Rainfall and runoff through all storm events 15 Figure 5: Schematic illustration of hydrograph separation analysis 16 Figuge 6: Characteristics of runoff components at study catchment 17 Figure 7: The relationship between quick runoff and rainfall 17 Figure 8: The relationship between delayed runoff and rainfall 18 Figure 9: Total suspend sediment and rainfall 19 Figure 10: The relationship between TSS and (a)runoff; (b) precipitation 20 Figure 11: The DO responses to rainfall 21 Figure 12: pH and rainfall in over time 22 ABSTRACT To evaluate runoff generation and water quality at a small forested catchment, we conducted and monitoring station, collected da from weather station and examined some water quality index (suspend sediment, DO, pH, Chloride, Nitrite, Sulfate) in Luot mountain at VFU in Xuan Mai town, Hanoi capital, Vietnam This study began form 17th July to 23th September Based on hydrographic analysis for nine storm events, we found that mean storm precipitation was 139 mm per storm Mean storm flow was 114 mm, corresponding to 82.3% of the runoff coefficient Total rainfall in over study time is 1248 mm where total runoff is 906mm The runoff coefficient is 72.6% The highest precipitation is 399mm (2sd to 5th September) when amount of runoff is 326mm The runoff coefficient is 81.7%; the lowest precipitation is 17mm while amount of runoff is 12mm This coefficient reaches 70.2% This study is a good way to assess the relationship between plantation and hydrological process, assessing the impact of plantation to water quantity and quality Findings of this study will provide an important scientific basis to enhance the protective function of forests planted for Vietnam I INTRODUCTION Water is one of the most important factors of natural resources which is necessary for human, ecosystem, and the economic development in mountain and non-mountain areas (FAO, 2005) However, the quantity and quality of fresh water not only in many regions of Vietnam but also in the world (Marzocchi et al , 2009) are increasingly endangered by overuse, misuse, pollution, and especially changing land cover caused by shifting cultivation It is increasingly recognized that both are strongly influenced by forests to water resource because forest maintains water quality through the stable soil, reduce erosion, sediment, and the pollutants from hill slope Forests also affect the amount of available water in keeping a canopy on rainfall, evaporation of moisture from the surface plant, maintain soil moisture, collect water from fog and maintain of soil infiltration rate They also affect the time of water transport by maintaining or improving the permeability and the ability to accumulate water in the soil (Bosch and Hewlett, 1982) Beside this, climate change is altering forest’s role in regulating water flows and influencing the availability of water resources (Bergkamp, Orlando and Burton, 2003) Moreover, with temperature climate and slope terrain the, threats of water degradation in Viet Nam is very serious Therefore, the relationship between forests and water is a critical issue that must be accorded high priority Management of forest resources has correlation relationship to water resource management and land conservation through changing the amount, timing runoff and soil erosion (FAO, 2005) Beside this the problems of controlling water quality and quantity, along with managing freshwater fisheries, have also become more complex (Valentinet at., 2008) The effects on the hydrological environment will significantly increase if no efforts are made to minimize the potential impacts Sustainable management of water catchments is one of the options that have to be considered to ensure all development activities have an acceptable impact on both water yield and water quality However, the lack of scientific information on catchment runoff is hindering the development of solutions and policies in environmental protection and the mitigation of natural hazards in Vietnam Therefore, to tackle these environmental issues, field-oriented observation is necessary In this context, we can assess and develop the management of water quality in forest catchment in Viet Nam The plantation area in Luot mountain of Vietnam Forestry University have been planted since 1984 when the school was arrived to Xuan Mai Forest ecosystems are planted at Luot mountain is a vital part of training to perform the tasks of the school In addition, since most appear plantation views have said that they are daily flow regulation and improve water quality for the region To understand the opinion of flow regime and water quality from plantation, we installed a monitoring station to measure runoff and precipitation in a 1.6ha mountainous forested catchment at Luot Mountain owned by Vietnam Forestry University, Hanoi and conducted the study entitled “Evaluating runoff generation and water quality at a small forested catchment” This study is a good way to assess the relationship between plantation and hydrological process, assessing the impact of plantation to water quantity and quality Findings of this study will provide an important scientific basis to enhance the protective function of forests planted for Vietnam II OVERVIEW OF THE PREVIOUS RESEARCH ISSUES 2.1 Overview Overland flow and water quality have been researched for many years in hydrology which was born in many years ago They are applied in producing and reached certain achievements The traditional hydrology developed Horton runoff theories in 1930s and 1940s to research surface runoff formation mechanism For 30 years of research ( Forster G R,1982) [31] Hibbert A R, (1967) [32], by the empirical observations which showed that rainfall intensity is usually smaller than the potential speed of water absorption in Forestry The Hydrology researches in slope terrain developed very fast and instead of ZHANG, 1989 [7] runoff super absorbent theory to form the runoff generation mechanism theories In recent years, there have been many overland flow research such as Moltranov.A.A.(1960, 1973), Matveev P.N (1973) Santra Reginal (1989), Giacomin (1662)(cited by Anh.K.P [11]… One of the most comprehensive researches which conducted in Russia, is Moltranov researcher He confirmed that, forest soil is possible to transfer water from surface water to groundwater where the area has 25o-30o of slope The drier soil effect of forest in Russia realizes not only in swamps but also in Middle Asia which has low rainfall In Africa, the first overland flow research was established by Hallet professor at Preotoria university in 1929 (Hudson,1981) Generally, Forest soil has high infiltration capacity and low overland flow appearance ( Douglass, 1977; Prichett, 1979) ( cited by Dien[5]) However, when forest are cut down to lead high slope and bare soil can make increase amount of water for overland flow (Ruxton BP, 1967 ; Imenson AC and VIS, 1982) ( cited by Dien [5]) One of the characteristics that related with runoff is permeable Darcy law’s is the typical research about infiltration Base on this, precipitation falls down directly to soil is very high This law proves that with higher infiltration the overland flow is lower Rainfall characteristic still affect to runoff In Australia, when Oloughlin researched Hydrology in eucalyptus forest, he concluded that overland flow has linear relationship with precipitation by the formation: y= a+bx; whereas x is precipitation, y is overland flows The results from previous studies in Vietnam and other countries in southeastern Asia showed a large difference in annual runoff coefficients (calculated by dividing annual runoff by precipitation) among countries and different regions within countries The biggest mean annual runoff coefficient was found in Vietnam (27.4%), while the smallest was found in Indonesia (2.1%) However, within a country, the annual runoff coefficient was very different across regions The mean annual runoff coefficients in Laos and the Philippines were 13.3 and 7.6%, respectively Potential reasons in among countries and regions are differences in catchment scale, annual precipitation, and/or land use type These findings suggested that the study site for our field trip studying water resource management in Vietnam had to be established in Vietnam itself because of the wide variety of runoff coefficients across regions In Viet Nam, runoff and erosion was researched in 1970s But from 1995 to now, this problem has concerned more and more The relationship between runoff and erosion has talked by Quynh and Dien(1991) One of the most important results is the overland flow quantitative formula for tropical forest like Viet Nam 2.2 Limitation of the previous studies Although there are many researches which study in runoff and erosion, are conducted by many professors in the world, but they still have some limitation such as:(1) Runoff generation and formation was studied a long time ago but the systematic hasn’t enough;(2) Most of studies just stop in description level and low quantitative and lack of Mathematic models to ensure confidence to descript runoff generation process On the other hand, Vietnam still uses old methods and equipment than other countries to measure runoff generation and lack of data water quality in forest catchment Carefully replace the stopper and shake to mix The Floe will dissolve and a yellow color will develop in the presence of oxygen This is the prepared sample 10 Fill the plastic measuring tube to the top with the prepared sample 11 Pour the contents of the tube into mixing bottle 12 Add Sodium Thiosulfate Standard Solution, 0.0109N one of drop at a time to the contents of the mixing bottle Swirl the bottle after each drop Count each drop Continue until the sample changes from yellow to colorless d Chloride Chloride was checked by titration measuring through steps below: Fill the mixing bottle to the 23-mL, mark with sample Add the contents of one chloride Indicator Powder Pillow, Swirl to mix Add Silver Nitrate Solution one drop at a time Swirl the bottle after each drop is added Count each drop until the sample changes from yellow to red-brown Total drops *12.5 = mg/L sodium chloride (NaCl) e Nitrite To measure Nitrite I did steps which are Rinse a viewing tube several times with sample, then fill to 5mL, mark Add the contents of one Nitriver Powder Pillow for 5mL sample Stopper the tube and shake vigorously for exactly 1min Allow this prepared sample to sit undisturbed for 10 not more than 15min Because no appearing pink color so after placing the tube into right opening of the Color Comparator, filling another tube the 5mL, mark with untreated sample so this is not the differences between tubes f Sulfate Here is sulfate test processing: Fill the sample mixing bottle o the 25mL mark 11 Use the clipper to open one Sulfaver4 Powder Pillows Add the contents of the pillow to the mixing bottle Press the cap on tightly and shake the bottle for 15s A white turbidity will appear if sulfate is present Allow the sample to stand 5min Invert the bottle to mix any solid left on the bottom Remove the capon the mixing bottle and slowly pour the contents into the clean 25mL graduated cylinder Hold the cylinder in the vertical position While looking straight down into the cylinder slowly insert the sulfate dipstick down into the cylinder until the black dot disappears completely Hold the dipstick in that position are rotate the cylinder and viewing the scale on the dipstick through the non-graduated portion of the cylinder Read the concentration by looking across the sulfate of the sample to the scale on the dipstick The number on the dipstick scale that meets with the surface of the sample corresponds to mg/L of sulfate in the sample If the black dot disappears before the first test mark( 200mg/L), the concentration of sulfate is greater than 200mg/L If the black dot does not disappears after the dipstick is inserted to the cylinder bottom, the surface concentration is less than 50mg/L 12 V RESULT AND DISCUSSION 5.1 Characteristic of runoff generation Figure Runoff generation in forested headwater catchment over time From this figure we can see that catchment runoff quickly responded to precipita tion inputs Increased rainfall intensity corresponded to increased runoff at catchments There were rain storms that I chose during the study time The range of precipitation ranged from 0.05 to 3.3mm when the range of runoff is from 0.02 to 1.8mm The highest rainfall is 3.3mm which belong in storm 9th where the runoff value is 1.8mm 13 Rainfall 50 100 150 200 Rainfall 250 300 a mm 350 Runoff 400 450 450 400 350 300 250 Runoff 200 b 150 100 50 Runoff coefficient % 100 90 80 70 60 c 50 Runoff coefficient 40 30 20 10 9storm event Figure 3.Characteristic of (a) Rainfall storm;(b) storm runoff;(c)Runoff coefficient in over storm event 14 Based on hydrographic analysis for nine storm events (figure 3), we found that mean storm precipitation was 139 mm per storm Mean storm flow was 114 mm, corresponding to 82.3% of the runoff coefficient Total rainfall in over study time is 1248 mm where total runoff is 906mm The runoff coefficient is 72.6% The highest precipitation is 399mm (2sd to 5th September) when amount of runoff is 326mm The runoff coefficient is 81.7%; the lowest precipitation is 17mm while amount of runoff is 12mm This coefficient reaches 70.2% We can easy the runoff generation trend depends so much on the rainfall When rainfall increases, the runoff increases When there is no rain, there is no runoff Runoff mm/Storm 350 y = 0.817x - 0.69 R² = 0.9645 300 250 200 150 100 50 0 100 200 300 400 500 Precipitation(mm/storm) Figure 4: The relationship between Rainfall and runoff through all storm events To check the close relationship between rainfall and runoff we can see figure When rainfall increases the runoff increases by the formula: y = 0.817x-0.69 with R² = 0.999 That means in small catchment, most of rainfalls become runoff 15 5.2 Runoff component Quick runoff = Storm flow Discharge (mm) Delayed runoff = Base flow Event Separation line Y  aT  b Quick runoff Delayed runoff Time (T) Figure 5: Schematic illustration of hydrograph separation analysis The separation line is Y=at+b where b is the first value Because this is a small and ephemerid catchment so runoff has components That why delayed runoff is the equal of runoff value minus quick runoff value Runoff has two components which are quick runoff(overland flow) and delayed runoff(base flow) (Figs: 6-8) Base flow comprised 53 mm (corresponding to 46.7% of storm flow)and overland flow comprised 61 mm (corresponding to 53.3% of storm flow) Overland flow was defined as that part of the runoff that enters streams during and immediately after precipitation via overland flow and fast subsurface flow Base flow was defined as slow soil water movement and bedrock outflow process in the forested catchment at Luot Mountain owned by Vietnam Forestry University, Hanoi 16 delayed runoff quick runoff Figuge 6: Characteristics of runoff components at study catchment Through the formula in Figure we can calculate the runoff components These separate runoff components enabled a qualitative evaluation of underlying dominant runoff pathways And we can see that percent of quick runoff is bigger than delayed runoff Quick runoff ranged from 38% to 62% where the range of delayed runoff is from 38% to 62% The mean of quick runoff is 52.7% where delayed runoff exposes 47.3% This suggested that overland flow is the dominant hydrological processes And we know that quick flow has the close relationship between erosion This is one of big problem we should concern 200 Quick runoff (mm/storm) 180 160 140 120 100 80 y = 0.4427x + 4.0952 R² = 0.9646 60 40 20 0 100 200 300 400 Figure 7: The relationship between quick runoff and rainfall 17 500 The fig is the way to examine the relationship between quick runoff and rainfall When runoff increases, quick runoff increases the value by the formula: y = 0.442x + 4.095 with R2 is so high R² = 0.964 Its mean this is the very close relationship The rainfall changes from 13mm to 399mm where quick runoff swing from 7mm to 166mm The mean of quick runoff is 61mm (53.3%) where mean of rainfall is 139mm We can say that quick runoff depends so much on rainfall 180 Delayed runoff(mm/stor m) 160 140 120 100 y = 0.3933x - 3.9799 R² = 0.8609 80 60 40 20 0 100 200 300 400 500 Rainfall (mm/storm) Figure 8: The relationship between delayed runoff and rainfall Through the fig 8, we can check again the relationship between delayed runoff and rainfall When rainfall ranged from 13mm to 399mm, base flow reaches from 38% to 62% The relationship formula between base flow is y = 0.393x - 3.979 with R² = 0.860 We can see overland flow depend more and more on amount rainfall The relationship between overland flow is close than base flow through R 18 5.3 Water quality and characteristic of catchment a Suspend sediment Standard TSS (B1) Figure 9: Total suspend sediment and rainfall Total suspended sediment (TSS) are particles that are larger than microns found in the water column Anything smaller than microns (average filter size) is considered a dissolved solid Most suspended solids are made up of inorganic materials, though bacteria and algae can also contribute to the total solids concentration 19 TSS is one of the most water quality measurements From fig 9, we can realize the TSS trend which depends more and more on rainfall When rainfall increases, TSS quantity increases The highest storm(399mm), the highest TSS value(97mg/L) The range of TSS is from 3mg/L to 97mg/L The mean of TTS is 35.7 mg/L The range of average of suspend sediment is from 0.261mg/L to 0.291mg/L All off storm events has lower TSS than TSS standard (for aquatic life).This is a good condition for aquatic life development Figure 10: The relationship between TSS and (a)runoff; (b) precipitation We know when rainfall increases, runoff increases Beside this rainfall and TSS has closed relationship Moreover, the relationship between TSS and total runoff is very closed when the trend line of TSS is the formula y = 0.166x1.084 with R² = 0.995 We can see TSS increases too when runoff increases I suggested that TSS depends on runoff When runoff increases TSS increases by the formula y = 0.277x1.022 with R² = 0.989 By this we can realize, the relationship between rainfall and TSS is closer than runoff and ones through R2 20 b Dissolved oxygen (DO) DO (mg/L) DO Standard (B1) Figure 11: The DO responses to rainfall As we know DO (Dissolved oxygen) exhibited a positive relationship with temperature but an inverse relationship with depth This can be explained by the higher photosynthetic rate accompanied by a higher light intensity in the upper water and a lower photosynthetic rate accompanied by organic matter decomposition in the deeper waters DO depend not much on runoff or rainfall Mean of DO in each storm ranged from 7.1 to 7.9 Beside this, all of sample in all storms has bigger DO than standard (B2 standard It is good for aquatic life) which is 21 c pH PH is the measure of the hydrogen activity in a solution It affects biological activity and lower pH increases solubility of metals in water PH is one of the important parameter to assess water quality It enables us to apply the suitable methods for water treatment or adjust the quantity of the substance in the water treatment process PH usually identify firstly to save time and money to take the suitable solution for treatment process Rainfall 50 100 150 200 Rainfall 250 300 350 mm/storm 400 450 pH QCVN 01:2009/BHYT QCVN 01:2009/BHYT 1 Storm event Figure 12: pH and rainfall in over time PH depends not so much on rainfall We can see that the highest pH(7.5) belong to highest storm event Of course we can’t conclude anything from this because I used pH indicator paper so it’s individually sensorial Beside this, all of sample of storm events doesn’t exceed pH standard which range is 6.5 to 8.5 for drinking water The lowest pH is Depend on pH parameter, water quality in this catchment is clear and ensure some human purpose such as for aquaculture 22 d Chloride, Sulfate, Nitrite Table 3: Parameters index Parameters SO4 (mg/L)