INTRODUCTION
Water is essential for life on Earth, circulating through land and the human body to transport nutrients and eliminate waste In Vietnam, the country boasts 2,360 rivers extending over 10 km, seemingly offering an abundant water supply However, inadequate infrastructure and financial resources lead to low utilization and uneven rainfall distribution, causing water shortages nationwide.
This research highlights the critical water issues in Vietnam, specifically in Hanoi, by examining changes in water surface area from 1994 to 2016 The findings aim to provide valuable insights into the evolving water landscape of Hanoi.
Hanoi, the capital of Vietnam, has experienced significant water surface degradation, with an alarming 80% reduction in water cover over the past 50 years Additionally, between 2010 and 2015, the city lost 72,540 m² of its water surface area, highlighting the urgent need for environmental conservation efforts.
Remote sensing technology has become integral to scientific research, offering powerful tools for in-depth exploration and assessment of Earth's natural resources This technology, combined with Geographic Information Systems (GIS), enables comprehensive studies such as mangrove environment assessments and forest classification surveys However, there is a notable lack of research focused on water cover changes in Hanoi utilizing GIS and remote sensing To address this gap, our study aims to apply these technologies to evaluate water cover changes in the region.
Water Cover Change in Hanoi City from 1994 to 2016 ”
Hanoi water surface cover is decreasing significantly over 22 years between 1994 and 2016
LITERATURE REVIEW Water surface related study
Hanoi is grappling with significant challenges in ensuring a reliable water supply for its growing population, as water resources are divided among households, industries, hospitals, and farms near urban areas Currently, groundwater serves as the primary water source, but its overexploitation necessitates the exploration of alternative water sources The city's rapid urbanization has outpaced the development of its water supply network, despite recent upgrades and expansions that have positively impacted the system As urbanization continues to evolve, the enhancement of the water supply infrastructure must also be an ongoing priority The management of water resources in Hanoi is not new; the city's Water Master Plan, created in 1986-87, was informed by data from Russian experts in the 1970s and 1980s.
The Hanoi Water Supply Programme (HWSP), initiated with support from the Finnish International Development Agency (FINNIDA) between 1985 and 1997, aims to improve water management in Hanoi Currently, funding for the water sector primarily comes from the World Bank, Asian Development Bank, and the Japanese Overseas Economic Co-operation Fund The Office of Transportation and Urban Public Works Service oversees water resources, supported by four key companies: the Hanoi Water Business Company, the Hanoi Sewerage and Drainage Company, the Environmental Company, and the Design Company for Urban Public Work Effective water management necessitates collaboration among these entities and the local population, yet the reliance on unmetered, subsidized water rates has hindered conservation efforts To enhance water management, Hanoi must prioritize integrated water management and foster a more engaged and informed user base, as current stakeholder interaction remains weak and public participation is limited.
GOAL AND OBJECTIVES
Study Goal
Assessing the water surface area change in Hanoi from 1994 to 2016.
Specific objectives
(i) Create maps of water surface area in Hanoi each year of 1994, 1998, 2000, 2005, 2010,
(ii) Analyze water surface changes in Hanoi in selected periods, namely 1994- 1998, 1998-
(iii) Make recommendations for better management of water surface in Hanoi.
SCOPE OF THE STUDY
To achieve the study objectives, a series of multi-temporal Landsat imagine from 1994 to
2016 is selected based on their availability on USGS website and qualities
- Spatial scope: the entire area of Hanoi city, captured in one Landsat image, is selected.
METHODS
Data collection
Interview data was gathered from individuals who reside in the study area, making it a valuable method for obtaining firsthand information Their deep understanding of the local context ensures that the insights collected are both accurate and beneficial for the research.
Investigate current status of water surface in Hanoi
Quantify water surface changes in Hanoi from 1994 to 2016
Identify key drivers of water surface changes over the study time in Hanoi
Propose recommendations for better management of Water surface in Hanoi
Figure 3.1 : method proportion of each objectives
Interviews provide valuable insights into the current status of land cover, management schemes, and the driving factors behind land cover changes To achieve effective results from these interviews, well-designed survey questionnaires were utilized.
In this study, GPS is used for marking points for image classification and checking accuracy of the study
3.1.3 Integration of multi-temporal Landsat data and GIS
The integration of multi-temporal remote sensing data and GIS effectively quantifies water surface changes in Hanoi from 1994 to 2016 This study provides a comprehensive overview of water surface changes over 22 years by creating individual land cover maps for the years 1994, 1998, 2000, 2005, 2010, 2013, and 2016, allowing for an evaluation of the status of water surface cover across these years.
Fig.3.2: Flowchart of methodology for image classification and change mapping
Clip study area Band combinations
Raster calculation Area of water surface cover
Land cover change during 4 periods 1994-2000; 2000-2005; 2005-2010; 2010-2016
This study utilized Landsat imagery from various years, including Landsat 5 TM from 1994, 1998, and 2000; Landsat 7 ETM+ from 2005 and 2010; and Landsat 8 OLI/TIRS from 2013 and 2016 These images can be accessed for free through the Landsat archive provided by the United States Geological Survey (USGS).
This study focuses on the northern region of Vietnam, where environmental factors like clouds and smog significantly impact satellite imagery Selecting cloud-free satellite images is essential for accurately analyzing water surface changes in this area To minimize variations in solar illumination and atmospheric conditions across different years, it is important to choose images acquired during the same time period Consequently, the research emphasizes using images from the dry season, specifically between November and March, to ensure consistency By analyzing satellite images from this 22-year period, the study aims to identify genuine changes in water surface levels.
STUDY SITE, NATURAL AND SOCIAL FEATURES
STUDY AREA
Hanoi, known as Hà Nội, is the capital and the second largest city of Vietnam, with a population of approximately 2.6 million in urban districts and 7 million in the metropolitan area as of 2009, growing to an estimated 7.7 million by 2015 Historically, from 1010 to 1802, it was Vietnam's most significant political center, although it was overshadowed by Huế during the Nguyễn Dynasty from 1802 to 1945 Additionally, Hanoi served as the capital of French Indochina from 1902 onwards.
1954 From 1954 to 1976, it was the capital of North Vietnam, and it became the capital of a reunified Vietnam in 1976, after the North's victory in the Vietnam War (Wikipedia)
The city lies on the right bank of the Red River Hanoi is 1,760 km (1,090 mi) north of Ho Chi Minh City and 120 km (75 mi) west of Hai Phong city
Hanoi has a warm humid subtropical climate (Köppen Cwa) with significant rainfall and four distinct seasons Summer, lasting from May to August, is marked by hot and humid conditions along with heavy rainfall Fall, from September to October, sees a drop in both temperature and precipitation Winter, from November to January, is typically dry and cool, with average sunshine of just 1.5 hours per day in February, often accompanied by cloudiness and fog.
Hanoi averages 1,680 millimetres (66.1 in) of rainfall per year, the majority falling from May to September There are an average of 114 days with rain
The average annual temperature is 23.6 °C (74 °F) with a mean relative humidity of 79% The highest recorded temperature was 42.8 °C (109 °F) on May 1926 while the lowest recorded temperature was 2.7 °C (37 °F) on January 1955
Hanoi, the capital of Vietnam, is situated in the northern region within the Red River Delta, approximately 90 kilometers from the coast The city features three primary types of terrain: delta, midland, and mountainous areas, with elevation gradually decreasing from north to south and west to east, averaging between 5 to 20 meters above sea level The northern and western parts of the city are characterized by hills and mountainous zones As the political center of Vietnam, Hanoi faces challenges due to rapid population growth, which exerts pressure on its aging infrastructure, much of which dates back to the early 20th century.
The population of Hanoians with roots spanning over three generations is quite limited compared to the city's total residents In the historic Old Quarter, once dominated by family-run businesses, many storefronts are now operated by merchants from other provinces Often, original families have either rented out their shops or relocated entirely This transformation has accelerated significantly following the shift from central-planning economic policies and the easing of the district-based household registration system.
Hanoi boasts the highest Human Development Index among Vietnamese cities and is projected by PricewaterhouseCoopers to be the fastest-growing city globally in GDP from 2008 to 2025 In 2013, Hanoi accounted for 12.6% of Vietnam's GDP, 7.5% of total exports, contributed 17% to the national budget, and attracted 22% of the country's investment capital.
5.1 Image Classification in this study, GPS is used for marking 30 points that are water surface cover( Rivers, Lakes and Ponds) and from the table below, I concluded that NDVI ranging from minus to 0.05 is defined as water
Number Latitude Longtitude NDVI Note
5.2 Changes in Water surface cover in Hanoi from 1994 to 2016
5.2.1 Thematic Water surface cover in Hanoi
5.2.1.1 Water surface covers in Hanoi in 1994
In 1994, water bodies accounted for 17% of the total study area in Hanoi, equivalent to 39,652.5 hectares, primarily located in the Northern, Eastern, and Southern regions, with a notable concentration in the Central part of the city Conversely, non-water areas comprised 83% of the land cover, totaling 199,132.2 hectares.
Figure 5.1 Thematic Land cover of Hanoi in 1994
5.2.1.2 Water Surface cover in Hanoi in 1998
In 1994, land cover patterns revealed that water bodies, including lakes, rivers, and aqua-cultural ponds, comprised 16% of the total study area, equating to 39,053.1 hectares, predominantly located in the Northern, Eastern, and Southern regions, with a higher concentration in Central Hanoi Conversely, non-water land cover constituted 84% of the total area, amounting to 199,731.5 hectares.
Figure 5.3 Thematic Land cover of Hanoi in 1998
5.2.1.3 Water Surface cover in Hanoi in 2000
In 2000, water bodies, including lakes, rivers, and aqua-cultural ponds, covered 16% of the total study area in Hanoi, equivalent to 38,620.8 hectares, predominantly located in the Northern, Eastern, and Southern regions, with a higher concentration in the Central part of the city In contrast, non-water land cover comprised 84% of the total area, amounting to 200,163.8 hectares.
Figure 5.5 Thematic Land cover of Hanoi in 2000
5.2.1.4 Water Surface cover in Hanoi in 2005
In 2005, water bodies, including lakes, rivers, and aqua-cultural ponds, covered 14% of the total study area, amounting to 33,594 hectares, predominantly located in the Northern, Eastern, and Southern regions, with a higher concentration in Central Hanoi Conversely, non-water land cover accounted for 86% of the total land area in Hanoi, totaling 205,190.6 hectares.
Figure 5.7 Thematic Land cover of Hanoi in 2005
5.2.1.5 Water Surface cover in Hanoi in 2010
In 2010, water bodies covered 10% of the total study area in Hanoi, amounting to 24,016.7 hectares, with lakes, rivers, and aqua-cultural ponds predominantly located in the Northern, Eastern, and Southern regions, but most concentrated in the Central part Conversely, non-water areas comprised 90% of the land cover, totaling 214,722.9 hectares.
Figure 5.9 Thematic Land cover of Hanoi in 2010
5.2.1.6 Water Surface covers in Hanoi in 2013
The coastal land cover map derived from the classification of Landsat 8 OLI/TIRS data from 2013 is depicted in Figures 5.11 and 5.12, as referenced in Figure 5.6 The analysis reveals that water surface cover accounts for only 9% of the total study area, which spans 22,605.8 hectares, while non-water areas make up the remaining 91%, totaling 216,178.8 hectares.
Figure 5.11 Thematic Land cover of Hanoi in 2013
5.2.1.7 Water Surface covers in Hanoi in 2016
The coastal land cover map derived from the classification of Landsat 8 OLI/TIRS in 2016 is depicted in Figures 5.5 and 5.6 As shown in Figure 5.6, water surfaces account for only 9% of the total study area, which encompasses 21,433.7 hectares, while the remaining 91% consists of non-water areas, totaling 217,350.9 hectares.
Figure 5.13 Thematic Land cover of Hanoi in 2016
5.2.2 Accuracy assessment of Water surface cover classification
In this study, I selected an NDVI range for water from -1 to 0.05 To verify the accuracy of this range, I evaluated 30 points in ArcMap, which confirmed the effectiveness of the chosen NDVI values.
Number Latitude Longitude NDVI Note
These 30 points showed as water in my Arcmap but actually there are 5 points is not actually water, it is kind of area that covered by water when exceed precipitation happen So the accuracy of this study is around 83%
5.2.2.2 Accuracy assessment by Google Earth
GENERAL CONCLUSION, LIMITATIONS AND FURTHER STUDY
General conclusion
This study aims to identify and analyze changes in water surface cover in Hanoi from 1994 to 2016 using multi-temporal Landsat data and GIS techniques By integrating remote sensing data with GIS methods, land cover maps for Hanoi were generated for the years 1994, 1998, 2000, 2005, 2013, and 2016, revealing significant land cover changes over the study period The accuracy of the analysis for the primary factor, water, is reported at 83%.
Between 1994 and 1998, the water surface cover in Hanoi experienced a slight decline of 1%, equating to a loss of 599.4 hectares From 1998 to 2000, the total water surface area remained relatively stable, with a decrease of 423.3 hectares However, the most significant reductions occurred between 2000 and 2005, and from 2005 to 2010, with declines of 2% (5,026.8 hectares) and 4% (9,532.3 hectares), respectively The trend of decreasing water surface continued from 2010 to 2016, resulting in an additional loss of 1% or 26,280 hectares.
During the study period, the total water surface area in Hanoi decreased by 10%, equating to 18,209.8 hectares, and represented a 46% reduction compared to the total water cover area in 1994.
In addition, promoting and enhanced international cooperation communicate and awareness-raising of local people, promoting scientific research, and solve environmental pollution
Satellite imagery and GIS techniques are essential for identifying and forecasting land cover changes driven by both human activities and natural factors As natural resources face increasing pressure, the integration of GIS and remote sensing has emerged as a significant advancement in the monitoring and management of these resources, especially in vulnerable areas.
Limitations
This study demonstrates that Landsat 8 effectively identifies land cover classes, achieving an overall accuracy of nearly 83% for water cover However, there are notable limitations due to the use of Landsat imagery as the primary data source for detecting land cover changes Variations in detection across different periods arise from the selection of imagery, which lacks consistent acquisition dates and seasonal alignment To enhance the accuracy of water surface area change detection, it is recommended that all satellite images be sourced from the dry season, specifically between November and March.
A significant limitation in accuracy assessment of land cover classification during the years 1994, 1998, 2000, 2005, and 2010 is the lack of reference data Additionally, the use of Landsat 5 TM and Landsat 7 ETM+ has resulted in misclassifications due to their low spatial resolution.
Further studies
This study utilized Landsat imagery for land cover classification, which, due to its 30m spatial resolution, yielded relatively low accuracy To enhance the quality of coastal land cover mapping in future research, it is recommended to employ higher spatial resolution satellites such as SPOT 6, SPOT 7, and QuickBird.
The limitation of time, data sources and satellite imagery are also limitations of this
From 1994 to 2016, various time frames (1994-2000, 2000-2005, 2005-2010, and 2010-2016) were utilized to monitor changes in water surface area This approach helps to identify overall trends in land cover changes However, future studies should incorporate additional years and time periods for a more comprehensive analysis of land cover change detection.