S Bengi

Head=6ft
Flow=3600gpm=60gal/s x 60seconds/min

Net Power =  1/10 x Flow x Head
Net Power = 1/10 x 3600gpm x 6ft
Net Power = 360 x 6
Net Power = 2160W (52KWH/day)

Net Power =  1/10 x Flow x Head
Net Power = 1/10 x 3600gpm x 40ft
Net Power = 360 x 40
Net Power = 14,400W (345KW/day)
(with this option you wouldn't really need a battery bank or inverter
https://www.micro-hydro-power.com/10kw-hydro-turbine-generator/

Based on just the stream banks. It would be easy for you to get a 3ft head.
Flow = 50cubic feet per second = 22,441 gallons per minutes
Head = 3ft

Net Power = 1/10 x Flow x Head
Net Power = 1/10 x 22,441gpm x 3ft
Net Power = 2,244 x 3
Net Power = 6,732W every hour
(If we disregard system losses the theoretically Power is actually twice what is listed above)


There are 24hrs in each day
Daily Production = Net Power x 24hrs
Daily Production = 6.7KW x 24hr
Daily Production = 161.6KWH per day
(If we use the high flow rate of 100cf/s vs the min of 50cf/s, we would actually double production)
(An avg USA house only uses 1/5 of that aka 33KWH/day or 1,000KWH/month), so even with a smaller head you would still be fine


Next would be to price out this system build:
Dam
Turbine/Generator
Controller
Dump Load
Battery Bank
Inverter

1) It's a great space is inside boston city limit, with a heavy deer/animal population, every winter.
2) The trees are not planted in the fall where the root system has a chance to become established.
3) The trees are planted in late spring/summer and they aren't watered to get them thru the 1st year
4) Native like pawpaw survive but European imports like apple/pear/plum are very suspectible to pest and die quickly

Because of the unique space, I would recommend the following.

1) Setup a drip irrigation system
2) Setup a dutch clover lawn that is 6inch, for nitrogen and also so that the edible can be easily identified and taken care of by the groundskeeper
3) Plant more natives like: blueberry, raspberry/blackberry, persimons, pawpaw, elderberry, native grapes, maypop, native hazelnut, etc
4) Plant more exotics like: mulberry, figs, goumi, akebia vine, artic kiwi vine, honeyberry, yellowhorn nut
5) Avoid the European imports like apple, pear, cherry, plum, peach, if you must plant the native or Asian species like beach plum, sand cherry, asian pear, etc
6) Don't accept the donation of half-dead trees in June and plant them
7) Plant in the fall for a better root system and less watering, and less deer/animal damage
8) Plant bare root, so that the plants are planted properly.

Seeing as how you aren't looking to live inside city limits. As a owner-builder, as long as you have 2x4 studs every 16inchs and a bit of insulation. They really dont care.

Now if you start telling them that you want to have a earthen roof and cob wall, and a composting tiolet and that you to run a DC only electrical system then you are just drawing attention to yourself and asking to be investegated alot more.

And yes as other have said, if you get somewhere with a house already you can probably renovate it and have it exactly the way how you want it.  If you buy raw land, just look out for impact fee. I have seen it cost $20,000

Harvesting rainwater is all about having the water serve multiple purposes, with less human inputs.
The rain can sustain the lifeform in the soil, which gives us nutriets for the plants and maybe even a microherd for chickens.

We will also need to water the soil less the more that garden naturally captures the water vs just letting it sheet away.
Its not only about capturing the water its also about not letting it disappear by mulching it either with green mulch or woodchip mulch.

Can you confirm that you were able to get 9ton of hay from  3acres. This averaging about 3ton per acre.
Of so that sounds just about right.  

A cow/animal unit will eat about 9,000lbs of hay per year. So your 18,000lbs of hay will feed about 2 cow/animal unit on the 3 acres of hayfield.

I feel uncomfortable saying that you can have 3 cows on 4 acres of pasture/hayfield. I think you a bigger area if you don't plan on importing any hay.

Maybe you can get away with 2cows and 5 sheep, with the expectation that you will have to buy a bit of hay from time to time.

Please note that a good amount of the hay will end up getting wasted and not eaten.

How many hay cutting do you do on the 3acres?
How much hay do you get per cutting and in total per year?

Once we know how much hay you produce we can then figure out how much your pasture will produce.

It probably safe to assume that you get 2.5ton of hay per acre per year aka 100 haybale. Which is about 3ton/6000lbs of pasture
https://www.nass.usda.gov/Charts_and_Maps/Crops_County/al-yi.php

In my area during the active growing season you probably need 3acres of pasture per cow-calf animal unit.
You will probable need another 3acres of hay/pasture for the winter season assuming you are in zone 6 vs zone 9 Florida or Zone 3 Wisconsin

There are things that we can do to increase the health and productivity of your pasture/hayfield.

I think that you should put down some landscape fabric and then 12inches of topsoil/compost.
The total area looks like it is only 40ft x 10ft, so it shouldn't take alot of topsoil

Personally the area is too small, I would focus elsewhere to plant a food forest

I am not too sure if septic tanks, solar panels and rain water catchment are considered earthship features. But I understand what you mean.
I would 1st figure out how much, water/electric/heat/etc you will need per day/month/quarter/year.
Next I would figure out how much you can produce on-site given your constraints.
I would then setup some backup systems in place.


SOLAR PANEL
Electricity, lets assume you follow the average and use about 1,000KWH per month or about 33KWH per day.
Daily Production = Daily Usage = 33KWH
Daily Production = Array Size x Solar Hours
33KWH = 10KW x 3.3Hours (4hrs probably turns into 3.3hrs after system losses)

10KW solar array is about 500sqft, so your roof is probably big enough.
Solar panels have heavy metals in them so I don't recommend drinking water from solar panels.

$5,000 Solar Panel 10KW
$2,500 Solar Panel Support/Misc 30panels
$10,000 Inverter/Charge Controller 10KW
$10,000 Battery Pack 33KWH
$5,000 Back-up Generator 10KW
$2,500 Fuel Tank


WIND TURBINE
A 1,500W wind turbine actually requires 27mph winds, and that is the wind that they assume that the site will have.
That same wind turbine in 10mph winds will only produce 150W per hour or 3.6KWH per day, and very few site actually posses the pitiful avg wind speed of 10mph.
So I normally don't recommend wind turbine. But lets say you threw caution to the wind and got 15,000W of wind turbine to compensate for the 10mph winds (aka you got ten 1,500W wind turbine)

$10,000 Generator 1500W @ 10mph (but 15,000W at its rated 27mph)
$6,000 Controller + Dump Load 2KW
$10,000 Battery Bank 33KW
$9,000 Inverter 10KW


HYDRO
Daily Usage = Hydro Production = Generator x Hours/Day = 36KWH = 1.5KW (generator) x 24Hours
Stream-Generator Net Production = Flow X Height X 1/10
1500W = 100gpm x 150ft x 1/10
1500W = 100 x 15
1500W = 1500W

$5,300 PVC Pipe+Weir/Dam+Misc
$2,200 Generator 1500W
$1,000 Controller + Dump Load 2KW
$10,000 Battery Bank 33KW
$9,000 Inverter 10KW


WATER SYSTEM
The average person uses 70gallons per day or 2,100gallons per month.
Water Production = Water Usage = 2,100gal/month
Water Production = Roof Size x Rainfall Amount x 1/2
2100gallons = 1000sqft x 4.2inch of rain per month x 1/2
2100gallons = 4200 x 1/2
(Maybe you will have a roommate or a partner or visits from family, so I would plan for a 2person household vs just one aka 4200gal/month vs just 2,100gal/month. If so you are going to need a much bigger roof.)

Water Usage
Toilets 18.5gal
Clothes Washers 15gal
Showers/Bath 12.5gal
Faucets 11gal
Dishwashers/Misc/Leaks 13gal
Total=70gal/day/person

There are two variable for micro-hydro power:
1) Height
2) Flow
Net Power = Flow (gpm) x Height (ft) x 0.1

So with a height of 100ft and a flow of 10gpm you could get
Net Power = 10gpm x 100ft x 0.1 =100W or (2400WH per day)

Actually height is usually a more limiting factor than flow.