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Baja Bio Sana – Site Development Field notes from June 23-26 2007 Andrew Jones
The notes below were developed during site visits with Geoff Lawton of the Permaculture Research Institute of Australia (www.permaculture.org.au), his wife Nadia Lawton and my wife, Shenaqua Sookhoo between the 23rd and 26th of June 2007. The site brief, as communicated with the group was to consider the following:
Planned Site Design Work The ‘client brief’ is that we are looking to develop the site to incorporate the following key features. 1. Vehicle access - all weather access for normal vehicles into main accommodation area (not just 4x4). 2. Maximize water-harvesting features on site so as to support biological production. 3. Siting of accommodation/built structures in order to maximize access to cooling breezes and other passive cooling features. consideration of partially buried structures and use of Roman cooling trenches. 4. Sitting of key infrastructure A. Common kitchen/admin space? What size/capacity? B. Number of dwelling spaces? What is their approximate footprint? C. Other types of potential infrastructure, listed out by function (several functions could be combined within one structure): 1. Multi-use space - healing, workshops, yoga, etc 2. Machinery/tool shed and laboratory space 3. Industrial scale food processing 4. Greenhouse/nursery 5. Composting and special soil preparation 6. Library and reading/research area 7. Administration 8. Camp kitchen, showers and compost toilet (first phase of operations) 9. Covered potable water storage tank 10. Covered irrigation water tank for drip irrigation (avoid current flood irrigation technique which is low efficiency)
The key activity during the consultancy was to consider the core earthworks needed to prepare the site for later stages of construction. We didn’t spend too long on the specifics of those phases as there are many considerations to be taken by the group. Once the key site patterns are properly identified and designed, other aspects of the design tend to follow, or grow out of them. Getting this aspect correct helps to harmonize the subsequent actions. Site Maps The site maps below details the boundary of the site, both the ‘main’ 15-acres of the current Baja BioSana owned land (main site), and the 5 acres to the north of proposed additional land to be purchased (5-acre site). The maps are oriented North.
Map 1. A contour map showing the two Baja BioSana Land parcels
Map 1 is a contour map – contours being lines of the same height above sea level marked on the map. The bottom contour line (brown), within the site boundary is marked at 175 meters above sea level. The next line to the north (orange) within the 5-acres is at 180 meters above sea level. Within the 5-acres, the northern contour line is at 185 meters, with the border of the land falling between the 185 m. and 190 m. contour line. Map 2. below allows us to see the physical features of the site. The entry road bisects the site running diagonally from right to left (SE to NW) from the entry gate on the lower southeast boundary. You can observe the orchard area of existing mango and avocado trees on the northern side of the main land parcel.
Map 2. Baja BioSana Land Boundaries with Google Earth Sat. Image The southern strip of the site is characterized by natural forest regrowth, which follows the slope where the land drops into the old river floodplain below. We have patches of land in the center of the site that have previously been cleared and grazed or cropped and are now revegetating. A second clump of natural vegetation occurs just to the east of the orchard. The 5-acre block consists of some large fruit trees on the western side of the block, a line of green vegetation on the northern boundary shows the line of the irrigation canal and the beginning of a steeper slope of the hill rising above to the north. The majority of the block has been cleared and is now undergoing natural re-growth. A significant feature to note is the arroyo (canyon or small drainage channel) that runs along the western boundary of the site. This runs water during wet times and storm events, and we will consider it within our overall design strategy since it represents both a barrier to entering our land during wet times, as well as a potential water harvesting resource. Key water Considerations Water represents a key element of benefit to the site. It serves multiple purposes – as an energy store when captured uphill, a carrier of nutrients to plants, a key element in support of vegetation systems etc. Water is a valuable resource, and in understanding it’s behavior within the unique patterns of the site, we can effectively harvest water that falls as rain, or is piped to the site. Some of this can be harvested in the future from rooftops as potable or drinkable water, the rest can be stored in the soil where it will support the growth of trees and other vegetation. Our basic approach is to try and get any water that reaches our site from any source (irrigation or rainfall, or piped water) to take the longest path with the most friction through the landscape. This will maximize the amount of time it spends in the landscape and the volume that infiltrates into the ground. The first step to understanding the site design in relation to water is to look at a survey map (Map 1). The survey lines on the accompanying map are at 5-meter (approximately15 feet) intervals, which mean that there is a vertical difference of that amount between lines. Water always runs at right angle to contour lines in the landscape – taking the most direct path downhill according to gravity. On Map 1, you can see the contour lines in relation to the site boundaries. Where contour lines are closer together, it means that the land has steeper slopes, where they are further apart, the land is flatter. These contour lines show us how the land is shaped and sloped and from this, we can see how to harmonize our design with those shapes to benefit from the water that reaches our site. We mentioned that a key objective is to slow water down in the landscape, there are a few more key principles to work with:
Annual Rainfall in Baja BioSana Area Before we look in detail at the harvesting of water, we need to understand what is the rainfall capture potential for the site? To understand this, we first need to consider how much rainfall there is for the area. The chart below for Santiago, close to our land, details the annual average temperature & rainfall pattern:
The chart for Santiago shows an annual average rainfall of 30.6 cm, or 12 inches. I have put the calculation for the site water capture potential in Appendix 1, the figures are summarized in the table below:
From this table, we can see that during an average year, we receive a total of 24.1 million litres (6.4 million gallons) that lands on the two parcels of land. Some of this evaporates, some infiltrates into the soil, some is transpired by plants, and some runs off during storm events – but we can appreciate that overall, the rainfall of the area is a significant resource.
It is significant in a second way for us also, if we look at an expanded map of our land and area, we can make some important observations. Map 3 shows us an estimated catchment area that feeds the arroyo running next to our land. This shows that an area of up to 200 acres north of our site forms the arroyo catchment above our site. Now we can begin to appreciate why this apparently small arroyo can push so many rocks downhill – during a rainfall event, particularly a storm all the excess water from the catchment area runs into the arroyo and a focused quantity of water running downhill carries a lot of energy. We can also see that this water comes off land that is apparently in a natural state and is not being farmed, so the water will be clean. We’ll consider in the next section how we might capture some of this water for use on our land.
Map 3. Arroyo Catchment Area
Key Water Harvesting Earthworks for Baja BioSana There is an opportunity to slow down the movement of water through our land, and to pull in additional water using two key earthwork strategies:
A. Gabions Gabions are leaky rock dams that may be built across the mouth of a seasonally flowing canyon or arroyo. Their purpose is to slow the flow of the water while it filters through the stones. This loss of velocity causes the water to drop the heavier particles that are being transported in suspension - eventually creating a flat silt field up to just below the height of the gabion wall and a small boulder field towards the back of the silt field (heavier objects drop out of suspension first). This silt field holds water in the silt, which is less affected by evaporation and moves more slowly downhill. The moisture in the silt field can better support the growth of vegetation, and moisture is released more gradually downhill. Gabions can also be used to divert excess flood flows into contour swale systems and spread the water out into the landscape. This will be described further below once we’ve described swales. A picture and illustration of a rock gabion is below.
Illustration 1. Gabion profile in cross section (top) and top view
Photo 1. Rock gabion in arroyo in Jordan
(photo courtesy of Geoff Lawton) B. Contour Swales A swale is a ditch where the material scooped out forms the mound. When this is done on contour, it forms a level, water-harvesting ditch with an earth mound below. The ditch interrupts the flow of water downhill (remember it is moving with gravity), and holds it, allowing it to absorb into the soil. Over time, it forms a plume of subsoil (underground) water. The lower mound of uncompacted soil provides a planting area. Depending upon the climate of the area, plants can be planted on the mound and into the lower end of the ditch (the drier the climate, the more planting is done initially in the swale ditch to reduce evaporation and water-stress on the plants). Contour swales recreate the effect of a forest root net by encouraging water to infiltrate into the soil. They are also tree planting strategies, with enhanced survivability of new trees planted into the system. The swale ditch is also a perfectly level path or track and in this way they can serve as the basis of a transport network through the site. These earthwork features are combined with the use of biological soil amendments like compost, and deep mulching to enhance survivability of the new plantings and build soil. Irrigation strategies includes drip irrigation for more efficient and directed use of valuable water resources. A diagram of a swale is below, along with some example photos of swales that were established in Oklahoma, USA, and former Yugoslav Republic of Macedonia.
Illustration 2. Swale diagram from Toby Hemenway (2001) Gaia's Garden: A Guide to Home-Scale Permaculture.
Photo 2. Freshly constructed swale in Oklahoma.
Photo 3. 8-month-old swale mounds stabilized with trees and herbs/grass in Macedonia. Proposed Swale and Gabion System Map 4, below, shows that there is an opportunity to construct a series of swales running through the two land sites. These can in a couple of cases, be linked via gabions to the arroyo running along the eastern boundary of the site. This will allow for capture of additional runoff water and infiltration into the site during rainfall events. The system including the additional 5-acres is shown.
Map 4. Proposed location of gabions and swales The order of construction for these features would be: a. Gabions, starting from the top (highest) gabion b. Starting from the top swale, construct swales, setting swale heights to harmonize with the pre-constructed gabions in the case of the two middle contour swales. In ‘picking up’ the gabion, the base of the swale is lower than the top of the gabion and the top of the gabion is lower than the top of the swale mound i.e. The top of the gabion is higher than the bottom of the swale trench but lower than the top of the swale mound (see illustration 1). Swales would need to be 1.2 meters in height (approximately 3’7”) to allow sufficient freeboard. In order to construct the gabions and swales, we’d need a 25-ton excavator, or D4-D6.5 with high track tilt and angle blade working within swale mound. Such tilt bucket machines are used on golf courses, so should be available in the region. Just below 180 m contour line is the key swale line (longest) that picks up arroyo and runs through the property. This can be varied by a couple of meters in practice on the site to assist in moving through the orchard. A key to success is the rapid stabilization of earthworks once these are completed. The initial seed planting following earthworks can be a cover crop (fast growing crop that puts nutrients and organic materials into the soil), such as cowpeas and sorghum. Following rain, the earthworks can be immediately planted with fast growing legume trees and bushes such as Glyrocidia, pigeon pea etc. These can then be interplanted with a selection of appropriate fruiting and other trees and bushes. As the climate of the area is hot and dry for much of the year, it will be necessary to utilize a strategy for minimizing evaporation and maximizing shading. In order to do this, thick mulch can be laid out around newly planted trees and gardens, and drip irrigation lines buried under the mulch in order to minimize evaporation and protect the water lines. Phases of Site Construction It would be ideal to complete the earthworks shown above as the initial phase of site development. Once these are in place, we can consider the next phases of site development. One of the initial decisions relates to the placement of initial infrastructure. Key placement factors
In order to facilitate site development, it is recommended that some collective accommodation is developed, along with a common kitchen area, compost toilets and shower facilities. In considering the above placement factors, we identified two potential zones for initial infrastructure development. These are shown on map 5 below.
In addition to this infrastructure, several other site elements also require consideration:
For those who are interested in learning more about compost toilet design and operation, I highly recommend Joseph Jenkins, The Humanure Handbook, A Guide to Composting Human Manure. It is now in its’ third edition, the second edition is available to read in full online at: http://weblife.org/humanure/default.html
Map 5. Proposed initial building site options The Baja BioSana site is located in an area of dry tropics, just north of the tropic of cancer. We literally cross this line between the airport and the land. As such, the area remains frost-free. The annual cycle of temperature and rainfall, as shown in the charts earlier, suggest that there are some key design features that should be considered in the design of any buildings or accommodation structures so as to maximize comfort in the climate. This remains hot and dry for a majority of the year. Other design considerations are strong winds associated with occasional hurricanes. We can always consider the extremes in our design approach so as to ensure stability and resilience when it really counts. In terms of local materials there is a locally abundant availability of river stone and river sand that could be used as a construction material. There are also local tree and palm timbers used in the construction of palapas according to their specific qualities of strength and flexibility. Another consideration is the linkage between building and gardens, and the use of specific strategies to help to provide cooling and shading for housing. Below are some specific design strategies, adapted from Geoff Lawton for design in the Dead Sea Valley in Jordan, with similar climatic conditions. Housing The house is an integral part of achieving a plentiful and productive garden design. It should be comfortable to live in, make efficient use of energy, and be inexpensive to operate. There are generalizations that can be made, but the essential design features required for a house in Southern Baja to perform efficiently in a passive way are quite specific. In general: · No Baja house should be planned or built without its integral trellis and garden, as these may not only save most or all energy usage and cost of air conditioning, but also provide food and shelter. The attached shade house in particular must be planned as integral to the house design and in fact, as the summer living area and kitchen. For this reason, the winter kitchen or indoor kitchen must open onto the shade house summer kitchen. · The house itself needs to be elongated east to west so that the shade that is cast on the north side is long and the heat gain on the west wall is small. While still permitting the low winter sun to enter the rooms through the south side windows, it is the roof overhang that excludes the summer sun from hitting the walls and windows. · The whole roof area should be completely shaded with a thick vine trellis, when ever possible. This insulates the roof, greatly reducing the heat gain of the house, making it cooler and more comfortable to live in. It also greatly increases the usable area of the house as the roof, once fully shaded, will become a very comfortable area open to breezes. Roofs have been traditionally used in many cultures for multiple uses. · Down drafts can be created with sails, slats, wind scoops and wind chimneys on roof areas, either fixed or self steering to force a down flow of the constant or prevailing winds. At their outlets in rooms, these down draft inlets can be fitted with damp hessian, damp trays of charcoal or unglazed pots full of water. These add considerable cooling capacity to the air and humidify the air inside the house. · Houses can be constructed so that they assist other houses, placed close together with the long axis of their street east west. A common or close-spaced wall ensures that neither wind nor heat can easily penetrate the settlement. If all houses are sun facing and of more than one storey in height, cool air in shaded narrow streets and courtyards is always available and vents at roof level will draw cool air into the rooms of the houses. The bottom floors and flat roofs are used for living and the upper floors and roof areas are for bedrooms. More specifically: West Side 1. No windows on the west facing wall of the house 2. The west facing wall should be painted white to reflect the late afternoon sun 3. If possible the west-facing wall should also be fully shaded with a deciduous vine trellis such as grapes, which will lose their leaves in winter and allow some extra light in during the cooler time of year 4. This west-facing wall vine trellis can, if possible, be incorporated into a courtyard design, with vine trellis above, and a small fishpond below. The light that is reflected from the white-painted walls creates a very comfortable private area in which to sit. 5. Evergreen trees should be planted to the west of the house to add to the shading and cooling of the house 6. North Side 7. Place a cool air source on the north side of the house in the form of a fully enclosed shade house created with thick vine trellis or shade cloth, if available. On the ground, add bark, leaf mulch or small stones to a depth of 150 millimeters, so that this area can be easily kept damp and cool on the shady north side, using very little water. This area is a source of cool air that can be vented into the house as a natural air conditioner and also makes a very comfortable outside kitchen and sitting area in summer.
South Side 1. A very simple sun chimney should be fitted to the south side of the house roof as the source of suction to pull the cool air through the house. This is made from a 150 mm diameter thin metal pipe 3 meters long, painted mat black with a rain cap on the top and an insect screen on the bottom. This pipe is then fitted to a hole made in the roof, connecting through to the ceiling of the hottest room on the south side of the house. This 3-meter sun chimney will need some form of bracing so that it does not blow over in the occasional strong seasonal winds. On hot days when the house is most uncomfortable, the hot sun shining on the mat black metal pipe will make it very hot, heating the air inside. This air will rise up the pipe, sucking the hot air from the house. 2. Close all windows and doors except the door leading to the cool shaded area on the north side of the house. The cool air is pulled into the house creating a comfortable living space with no energy cost involved. Uninterrupted air flow is very important. The total cooling effect can be greatly increased if unglazed pots full of water are placed in the airflow, as the evaporation cools the living space further.
Windows 1. The west side of the house should have no windows because the low westerly sun is the greatest source of heat in the house. 2. The east side can have small windows. It is best if they are partly shaded with about 50 percent, full-length shade cover. 3. The north side has the cool shade house attached and only needs access with small windows and some form of insect-screened venting close to the floor for the cool air flow input pulled by the solar chimney on the south side. 4. The south side, facing the sun, should have no more than 25 percent of the total wall area in windows and should have overhanging eaves of at least half a meter wide to protect from mid-day mid-summer sun. 5. External, rather than internal blinds prevent most heat entry through windows. These can be made of wood, aluminum, or cane matting and rolled up under the overhanging eave when not needed.
Garden Design Long term health and good nutrition for can be achieved for the family through home gardens. A mixed garden of vegetables, herbs, fruit, and small animals produces all the essential minerals and vitamins needed and can make every family self-reliant. The garden must be planned very seriously if it is to be successful and to be so, it must not only be very productive, but must also continuously increase in soil fertility and produce with less and less effort over the first 10 years. This is possible and quite easily achieved if you follow the instructions below carefully. Generally: 1. Mulch is the most important ingredient in good garden design and it is the one element that is completely missing from almost all local gardens. Yet a well-mulched garden (100 to 150 millimeters thick) uses 1/10 the water of bare soil. That is, bare soil gardens use 10 times more water to produce the same volume of crops. Garden beds need to be completely covered in thick mulch continuously, so mulch will need to be sourced locally and eventually produced locally in surplus, which can easily be achieved. 2. It is important that the garden be well fenced for its protection from many different types of local foragers. 3. Vegetables can be produced on slightly raised garden beds using many different materials for the edging, such as stone, concrete blocks, logs, and banana trunks. Mud bricks also work very well as they absorb some water and insulate the garden bed, cooling it down and reducing its water requirement. Mud bricks are also very cheap to make. 4. For best results, all vegetable gardens will need to be at least 75-percent shaded. This can be done individually with shade cloth, palm fronds, or tree branches on frames 1 to 1.5 meters high. Alternatively, solid pillars of concrete blocks, wooden posts, steel posts or mud bricks to 2.5 meters can be used to produce permanent vine trellis crops over most of the garden. Grape vines trellises with overhead spacing of 1 to 2 meters will shade a vegetable garden very well, relieving excess sun burning and water stress. Specifically, 1. The east side of the vegetable garden needs to have a vertical or angled out trellis with 300 millimeter spacing of uprights and horizontals that can be densely planted in productive crops of climbing vegetables, tomatoes, cucumbers, beans, gourds etc. This will protect the garden from the early morning sun, which can dry the moisture left from the cooler nighttime temperatures. This will keep the garden cooler for longer at the start of the day and reduce overall water stress. 2. The west side of the garden needs vertical or angled out trellises with 200 millimeter or less spacing of uprights and horizontals covered with a very dense and very shady planting of thick fleshy vines, as great heat can build up in the late afternoon and cause severe water stress. 3. The north side does not need a vertical trellis and can be left completely open, as this is the shady side and receives no direct sun. 4. The south side should have a vertical or angled out trellis with wide spacing of 1 meter, with uprights only, and planted with a productive climbing vegetable crop. Increasing soil fertility To insure that garden fertility is continually increasing, the following steps should be taken: 1. The continuous additions of mulch will allow a steady increase in the fertility and productivity of the garden. Many different materials can be used for mulch but most importantly, all crop residues produced from the garden must be returned as mulch to the garden. Additions of leaves, weeds twigs, kitchen food scraps, cotton clothes, wool, small branches, rotten wood, bark, wood chips, saw dust, paper, card board, hair, feathers, skins, and bones are all organic materials that will decompose into high quality organic black humus. This will greatly increase soil fertility and water holding capability, if added to the surface of the soil in high enough quantity (100 to 150 millimeters deep), especially if some animal manures are incorporated in the mix. Mulch needs to be absolutely soaked initially. After that, slight additions of water daily will help retain good moisture for both mulch decomposition and crop growth. 2. Any design feature that can increase the amount of mulch the garden can receive will potentially increase the garden’s soil fertility. Areas of the garden can be maintained as mulch pits. They should be kept full and piled as high as possible so that the mulch is continuously rotting down to high-quality black organic humus. These mulch pits become very fertile to plant around and after a few years become very fertile circular vegetable gardens. Animal waste in the form of meat, fish and even whole dead animals can be buried deep in the mulch pits at least half a meter deep. This will quickly decompose, and speed up the decomposition process of the surrounding mulch. 3. The garden should be continuously growing crops and never be left empty. This is essential in creating ongoing increases in soil fertility and in providing shade to the soil. 4. It is important to design the garden so that beds are not walked on. Walking on the vegetable growing bed causes soil compaction and greatly reduces soil fertility and productivity. Therefore, beds must be designed so that footpaths allow access to the entire vegetable- growing area. The widest you can have a good productive vegetable garden growing bed is twice the length of your arm. A footpath on both sides of the bed allows you to access the entire bed-by reaching halfway into the bed from either path. This is called a double-reach row bed. Once you have this design in place, there is never a need to walk on the garden bed where the crops are grown. 5. In the original construction of the garden the garden must be shaped so that it will hold water and can be flooded to a depth of 100 to 150 millimeters of water. This is important so that the water will sit in the bed before it soaks in. This same shape and space will also hold the mulch 100 to 150 millimeters deep and will hold the mulch and water at the same time. 6. A diversity of crops should be planted that are appropriate to the season. They should be completely mixed in the planting bed as much as is practical, with mixed perennial herbs around footpath edges and corners. Rosemary, oregano, mint, chamomile and many more herbs are traditionally grown and used locally. When incorporated into the home vegetable garden, they not only confuse and distract pests they also add stability and increase fertility. 7. All vegetable garden growing beds should have a regular succession of bean crops. This will help maintain soil fertility, as these legumes add nitrogen to the soil. Broad beans and peas should be grown in winter, and bush beans, tropical beans and snake beans in summer. 8. All wastewater except that from the toilet must be directed to the garden. If natural cleaning soaps are used in the house, then all shower water, wash basin water, kitchen sink water and water used to wash floors is good for the garden; in fact the average volume of water from these sources that would otherwise be wasted per person will grow the food for that person if gardens are well designed and deep mulches are used. Natural Fertilizer Fertilizer can be made by mixing mulch, manure and soil. First, mix 9 parts mulch with 1 part manure. Manures vary in strength with the strongest being pigeon then chicken, turkey, duck, goose, rabbit, cow, goat and sheep. The more variety of manures and mulch materials that are used, the better the potential soil fertility. Next, mix fine soil in with the mulch manure mixture at about 1/20 fine soil to 19/20 mulch manure mixture. After applying this mixture to the garden, add a layer 10 millimeter thick of fine soil on top of the mixture. Orchards Fruit trees that are often grown in local gardens include date palms, figs, guava, avocado, pomegranate, grapes, citrus, carob, mango, white, black, and red mulberries, loquat, banana, papaya, fruiting cactus (Tuna spp), sugar cane and custard apple. An extensive list of possibilities can be developed for the site working cooperatively with Gabriel and Kitzia Howearth at Buena Fortuna Botanic Gardens in La Ribera – about a 25-minute drive towards the coast from our site. All fruit trees benefit greatly from deep mulch surrounding their trunks but not touching the trunk. Tree mulch is constructed exactly the same as vegetable garden mulch with the same water holding soakage beds around the tree trunk, though it can be rougher and contain larger material. It should be placed in a circle from 25 millimeters away from the trunk out to the outside drip line from the tree canopy, and should be applied in a thicker layer than vegetable mulch—200 to 500 millimeters thick. Animal wastes or carcasses such as road kills can also be buried, under newly planted trees, adding a slow release organic fertilizer to the new planting. An excellent way to help tree mulch to retain moisture is to plant succulent ground covers like pig face (Mesembryanthemum spp.) and sun jewel on the inside and the outside of each tree mulch circle. These succulent plants become living ground covers that insulate the soil. Included in many gardens are many varieties of legume trees which are often known for being good forage for animals. Though it is not widely known, these trees act as natural organic fertilizers to the soil if their leaves, seeds, seed pods, twigs and rotting wood are allowed to remain on the soil as mulch. In addition, leguminous trees can be planted in close association with mixed fruit trees. Large amounts of natural organic nitrogen are released from the roots deep in the soils, which then become available to the fruit trees, especially after being cut back. When these trees are cut for animal forage or for mulch many of these trees will re-grow so that they continuously produce mulch, animal feed and soil fertilizer. If cut back at the right time of year–with the very first light rain of early winter to mid-winter, they open up the garden for extra winter light and warmth when it is needed. After this, all cutting must stop for the trees to recover and be able to provide their much needed summer shade.
In the case of Jordan, the most functional
of all these trees grown locally is Leaucaena, but Albizia lebek and Tipuana
tipu are growing in some locations. Prosopis is very common and is very hardy
but is very thorny as is the local legume tree jerusalem thorn (Parkinsonia spp),
Poinciana is also grown in many gardens but it is a little bit slow-growing to
be used as a cut mulch tree and is better as a shade legume tree and fruit
tree-associated plant. There are 2 types of Acacia grown locally and a
Casuarinas. These are good soil nitrogen-producing fruit tree-associates for
adding natural organic fertilizer to the soil but are not good at recovering
from cutting. The most appropriate local nitrogen fixing species for the Baja
BioSana site can be developed again with the assistance and expertise of Gabriel
and Kitzia Howearth from their experience at Buena Fortuna. Appendix A – Site Water Capture Potential Rain ‘Income’ Land Area First parcel (5.85 ha – 14.46 acres): 58,500 m2 Additional (2.023 ha – 5 acres): 20,234 m2
Annual Average Rainfall: 306 mm/12.05 inches Baja Biosana Main Site = 58,500 x 306 mm = 17,901,000 litres/year Additional 5 acres = 20,234 x 306 mm = 6,191,604 litres/year
The above table shows the total rainfall that will fall on the Baja BioSana land parcels in an average year. The behavior of this water will depend on whether it falls in a major rainfall event, where the ground gets saturated – resulting in significant runoff, or smaller events where much of the rainfall is absorbed into the soil. Watershed Runoff Water flows within a watershed, that can be assessed on different scales. In the case of our land, the amount of land above our northern boundary that is higher than our land will contribute to water flows through our site, depending on which way the land slopes. There is evidence of a small irregularly flowing channel that flows through the middle of the main site, showing that there are times of suface water flow across the land. It is likely that this becomes active during rainfall events during the peak rainfall months of Aug, Sept, Oct. A significant arroyo running just outside the eastern boundary of the site is likely to run occasionally over the same period and during storm events throughout the year.
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