#73: Examining the Pakistan Floods of 2022 and Land Regeneration Strategies - Part II
In #72, we analyzed the devastating impact of the 2022 Pakistan floods and highlighted the pressing need for effective land regeneration strategies to manage future rainfall and mitigate flood risks. We discussed the importance of natural regeneration and riparian buffers in controlling water flow and enhancing the resilience of flood-prone areas.
The 2022 floods were among the worst in Pakistan's history, causing widespread destruction across multiple provinces. The extreme precipitation events over a 15-day period overwhelmed the existing infrastructure, displacing millions of people and causing economic losses amounting to billions of dollars. The floods exposed the vulnerability of our current flood management systems and underscored the necessity for sustainable, nature-based solutions.
In today's post, we will delve deeper into the quantitative aspects of these strategies. Specifically, we will provide a detailed analysis of how riparian buffers, with varying widths and infiltration rates, can manage significant volumes of floodwater. By examining these metrics, we aim to demonstrate the potential of riparian buffers not only to mitigate flood impacts but also to provide a range of ecological benefits.
Our focus will be on the practical implementation of riparian buffers and how they can be scaled up to handle the kind of extreme weather events experienced in 2022. We will use real data from the affected provinces to calculate the volumes of water that can be managed through these natural systems. Furthermore, we will discuss additional merits of these buffers, such as improved water quality, enhanced biodiversity, and increased groundwater recharge, which collectively contribute to the overall resilience and sustainability of our landscapes.
Background knowledge
Riparian buffers demonstrate exceptional potential for groundwater recharge, often showcasing infiltration rates significantly higher than adjacent agricultural or urban lands. A study in the Midwestern USA found these rates to be five times greater, highlighting their capacity for groundwater replenishment (Bharati et al., 2002).
Further research has shown that riparian buffers effectively reduce pollutants like nitrates while enhancing groundwater recharge. For instance, a study on saturated riparian buffers in Iowa found substantial nitrate removal and improved recharge through managed infiltration (Jaynes & Isenhart, 2019)
Recharge rates in these buffers, though highly variable and influenced by seasonal shifts, can be substantial. Research indicates rates as high as 50-60% of infiltrated water during wet seasons, depending on soil saturation and vegetation cover (King et al., 2016).
In various studies, observed infiltration rates in riparian buffers have varied widely:
Lowest: Approximately 16 cm/hour in grass buffers with compacted or less permeable soils.
Highest: Up to 41 cm/hour in forested buffers with well-structured, organic-rich soils.
Average: Typically around 26-30 cm/hour in mixed vegetation buffers with moderate soil permeability (Frontiers).
This variability underscores the importance of tailoring riparian buffer design and management to local conditions to maximize their effectiveness in groundwater recharge and pollution mitigation.
Check out the previous post which talks about Riparian Buffers
A - Data Recap
To understand the scale and impact of the 2022 floods, we first need to look at the rainfall data across Pakistan. During the 15-day period from August 15 to September 1, 2022, Pakistan experienced extraordinary rainfall events. The average cumulative rainfall during this period was significantly higher than typical seasonal averages, which contributed to the severe flooding.
Here's a detailed breakdown of the average cumulative rainfall in each province:
Rainfall
Punjab: 350 mm
Sindh: 500 mm
Khyber Pakhtunkhwa: 400 mm
Balochistan: 300 mm
Gilgit-Baltistan: 200 mm
Azad Jammu and Kashmir: 450 mm
This rainfall data, sourced from the Pakistan Meteorological Department (PMD), highlights the uneven distribution of precipitation, with Sindh and Azad Jammu and Kashmir receiving the highest rainfall.
Total Area of Each Province:
Understanding the total area of each province is crucial for our calculations, as it allows us to determine the volume of water each region received during the flood period.
Punjab: 205,344 km²
Sindh: 140,914 km²
Khyber Pakhtunkhwa: 101,741 km²
Balochistan: 347,190 km²
Gilgit-Baltistan: 72,971 km²
Azad Jammu and Kashmir: 13,297 km²
By combining the rainfall data with the area of each province, we can calculate the total volume of water that fell in each region. This helps us to better understand the magnitude of the floodwaters and the need for effective management strategies.
Total River Length by Province:
Rivers play a vital role in the hydrological dynamics of an area. The length and distribution of river networks within each province significantly influence flood behavior and the potential effectiveness of riparian buffers.
Punjab: 6,465 km
Sindh: 926 km
Khyber Pakhtunkhwa: 1,340 km
Balochistan: 1,256 km
Gilgit-Baltistan: 1,645 km
Azad Jammu and Kashmir: 1,120 km
This river network data, compiled from various hydrological studies and governmental reports, provides the foundation for our buffer zone calculations. The extensive river systems in Punjab and Gilgit-Baltistan, in particular, highlight the critical areas where riparian buffer zones could have a significant impact on flood management.
Detailed River Network
Understanding the river networks within each province is crucial for planning effective flood management strategies. These networks determine how water flows across the landscape and where riparian buffers can be most effectively implemented.
Punjab
Punjab, with its extensive network of rivers, is significantly impacted by flooding. The major rivers in Punjab, Pakistan are:
Indus: 1,100 km, originating from the Tibetan Plateau and flowing into the Arabian Sea.
Jhelum: 725 km, originating from Verinag in Jammu and Kashmir and merging with the Chenab River.
Chenab: 960 km, originating from Himachal Pradesh in India and joining the Indus River.
Ravi: 720 km, originating from Himachal Pradesh in India and merging with the Chenab River.
Sutlej: 1,450 km, originating from Lake Rakshastal in Tibet and flowing into the Panjnad River.
Beas: 470 km, originating from Beas Kund in Himachal Pradesh and merging with the Sutlej River.
Swan: 250 km, originating from Murree in Punjab and joining the Indus River.
Haro: 70 km, originating from Abbottabad in Khyber Pakhtunkhwa and merging with the Indus River.
Kurram: 320 km, originating from the Spin Ghar mountains in Afghanistan and merging with the Indus River.
Gomal: 400 km, originating from Ghazni Province in Afghanistan and merging with the Indus River.
The total length of the river network in Punjab is approximately 6,465 km.
Sindh
Indus: 700 km, originating from the Tibetan Plateau and flowing into the Arabian Sea.
Nara Canal: 226 km, originating from the Sukkur Barrage and flowing into the Thar Desert.
There are some other canals but, the length could not be verified.
The total river network length in Sindh is approximately 926 km.
Khyber Pakhtunkhwa
Swat: 240 km, originating from the Kalam Valley in Khyber Pakhtunkhwa and merging with the Kabul River.
Gomal: 400 km, originating from Ghazni Province in Afghanistan and merging with the Indus River.
The total river network length in Khyber Pakhtunkhwa is approximately 1,340 km.
Balochistan
Balochistan, despite being an arid region, has several important rivers:
Hingol: 560 km, originating from the Central Makran Range and flowing into the Arabian Sea.
Dasht: 346 km, originating from central Balochistan and flowing into the Arabian Sea.
Rakshan: 350 km, originating near Nushki in Balochistan and merging with the Mashkel River.
The total river network length in Balochistan is approximately 1,256 km. There are some other rivers as well, if they are added the length becomes 2558 km.
Gilgit-Baltistan
Gilgit-Baltistan, known for its mountainous terrain, has several rivers that are crucial for the region's hydrology:
Indus: 500 km, originating from the Tibetan Plateau and flowing into the Arabian Sea.
Shyok: 550 km, originating from the Rimo Glacier in the Karakoram Range and merging with the Indus River.
Gilgit: 240 km, originating from Shandur Lake in the Hindu Kush and merging with the Indus River.
Hunza: 190 km, originating from the Khunjerab Pass in the Karakoram Range and merging with the Gilgit River.
Naltar: 55 km, originating from Naltar Valley in the Karakoram Range and merging with the Gilgit River.
Astor: 110 km, originating from the Deosai Plains in the Karakoram Range and merging with the Indus River.
The total river network length in Gilgit-Baltistan is approximately 1,645 km.
Azad Jammu and Kashmir
Azad Jammu and Kashmir, with its rugged terrain, has several key rivers:
Jhelum: 725 km, originating from Verinag in Jammu and Kashmir and merging with the Chenab River.
Neelum: 245 km, originating from Indian-administered Kashmir and merging with the Jhelum River.
Poonch: 150 km, originating from the Pir Panjal Range and merging with the Jhelum River.
The total river network length in Azad Jammu and Kashmir is approximately 1,120 km.
B- Calculations
In this section, we provide a detailed analysis of the water volumes involved in the 2022 floods and how riparian buffers can be utilized to manage these volumes effectively. The calculations below use the average cumulative rainfall data, total area of each province, and river lengths to determine the potential water management capacity of riparian buffers.
Total Volume of Water for Each Province
Here are the daily volumes for all provinces:
Punjab: 4.79136 BCM/day
Sindh: 4.69427 BCM/day
Khyber Pakhtunkhwa: 2.71196 BCM/day
Balochistan: 6.94380 BCM/day
Gilgit-Baltistan: 0.97295 BCM/day
Azad Jammu and Kashmir: 0.53268 BCM/day
Volume Managed by Buffers
Let’s assume that the total buffer width is 100m, we are taking the infiltration rate of 26cm/hr - In studies on riparian buffers, the infiltration rates can vary widely depending on factors such as soil type, vegetation, and land management practices. Here are the infiltration rates observed:
Lowest rate: Approximately 16 cm/hour, typically found in grass buffers with compacted or less permeable soils.
Highest rate: Up to 41 cm/hour, found in forested buffers with well-structured soils and high organic matter content.
Average rate: Generally around 26-30 cm/hour, which is a common rate for mixed vegetation buffers with moderate soil permeability (Frontiers).
Also, Forested buffers generally showed good nitrogen removal efficiency, with various vegetation types contributing differently to nitrate and phosphorus removal. For example, grass/forest buffers required widths of 23 m for phosphorus and 130 m for nitrogen to achieve 50% removal efficiency (Cao et al., 2018).
Based on such studies, we are aiming for a buffer width of 100-200m and recommending forested buffers for faster infiltration rates.
Here is a calculation for an infiltration rate of 26cm/hr (6.24m per day)
Based on this, using river length and a buffer length of 100m as a standard we get the following data for all the provinces.
This table shows that, while riparian buffers with a width of 100 meters on each side of the river can manage a significant portion of the rainfall, additional measures may be required to handle the excess water, particularly in provinces like Sindh and Baluchistan i.e. allocation of more land to regenerative riparian and riverine ecosystems in Sindh and Baluchistan by increasing the buffer length.
To manage that, something like this would be needed, expanding the riparian buffer and riverine forest zones to 812m buffers along the river or having 100m buffers along the river and an additional 712m of natural forests at appropriate places in the watershed, For balochistan nearly 991m width of riparian buffers along it’s rivers are required. In KPK, a buffer width of 150m would suffice.
Enhancing the buffer widths further leads to more infiltration, and cleaner water. for example a buffer width of 200m gives us,
Significantly, increased water handling capacity.
Volume Managed by Different Buffer Widths and Infiltration Rates
With infiltration rates of 30cm per hour and 41cm per hour, we have the following metrics for Punjab.
The chart includes three different infiltration rates:
26 cm/hr (6.24 m/day): Represented by the yellow line.
30 cm/hr (7.2 m/day): Represented by the orange line.
41 cm/hr (9.84 m/day): Represented by the pink line.
As the buffer width increases, the volume of water handled also increases. This relationship is more pronounced at higher infiltration rates, demonstrating the potential effectiveness of improved infiltration rates in managing large volumes of floodwater.
Riparian Buffer Area as Percentage of Total Area
To contextualize the scale of these buffer zones, we calculate their area as a percentage of the total area of each province when a 100-meter buffer width is used:
For Sindh and Baluchistan we need to increase the area 10 times to handle the volume we had in 2022 Floods, which will bring the total percentage to 0.6% and 0.3%. To be on safe side, we can safely assume that a mere 1% of total area of Pakistan, allocated to Riparian Buffers and Riverine Forest Ecosystems will safeguard Pakistan from future climatic shocks.
Conclusion
Restoring and expanding riparian buffers can significantly enhance Pakistan's resilience to floods, improve water quality, and promote ecological health. For example, a 200-meter-wide riparian buffer along Punjab's river network (just 0.6% of the province's area) could potentially manage 12.7 billion cubic meters (BCM) of water, equivalent to 3.6-4.5% of Pakistan's annual water budget. This would also enable substantial groundwater recharge, adding 3.81 to 8.89 BCM of clean water to Punjab's aquifers, representing an additional 6.67% to 14.81% recharge. A nationwide program could magnify these benefits tenfold.
Additional Benefits of Riparian Buffers
Cleaner Water: Filters out pollutants, improving water quality.
Increased Biodiversity: Enhances habitats for diverse flora and fauna.
Fish Habitat: Provides critical habitats for fish.
Economic Benefits: Supports fishing and agriculture through improved water quality and habitats.
Increased Rainfall: Forested areas contribute to precipitation patterns.
Cooler Temperatures: Vegetation mitigates the urban heat island effect.
Enhanced Water Availability: Improves both groundwater recharge and surface water storage.
Groundwater Resources in Pakistan: A Brief Overview
While Pakistan's Indus Basin aquifer has a vast storage capacity (estimated at 12,500 BCM), only 10-20% (1,250 to 2,500 BCM) is realistically usable due to depth and quality constraints. The country's annual groundwater recharge (55-60 BCM) is roughly equal to its extraction rate, emphasizing the need for sustainable management and recharge efforts.
Key Insights and Typical Values:
Enhanced Infiltration: Riparian buffers significantly increase infiltration rates compared to adjacent areas.
Groundwater Recharge Efficiency: This can range from 40-70%, particularly high in sandy or loamy soils.
Seasonal Variability: Recharge rates fluctuate seasonally, with higher rates during wet periods.
This analysis demonstrates the potential of natural regeneration, specifically riparian buffer restoration, to address Pakistan's flood challenges and improve water security. A nationwide approach could substantially augment these benefits, providing a sustainable solution for a pressing issue.
Thank you for reading!
References:
Pakistan Meteorological Department (PMD)
National Disaster Management Authority (NDMA)
Provincial Irrigation Departments