Water and Development
Part 3a: Watersheds
Milind Sohoni
www.cse.iitb.ac.in/∼sohoni email: sohoni@cse.iitb.ac.in
Objective
Supply, demand and Allocation
Surface water, groundwater, reservoirs and other structures.
Complex domain with multitude of interactions.
How do we simplify the domain for better analysis?
Structural decomposition
Domain Decomposition-By surface flows
p1
p2
p3
p5 p4
surface water
A1 A2 A3
A4 A5
salinity
ingress water table
q
W(q) W(p2)
The watershed W(x) of a pointx is
W(x) ={all points y from where surface water flows to x}.
For any two points x,y either W(x)⊆W(y) or W(x)∩W(y) is a thin set.
Decomposition of Domain into disjoint union of watersheds.
The Watershed
Thane Watersheds
Ridgelines, flowlines, drainlines
How does water flow on a slope?
flow of water surface normal
iso−height
gravity water drop
Elevation e(x,y), then flow direction is∇e = (−∂e∂x,−∂y∂e) and normal is [−∂e∂x,−∂y∂e,1]. Direction of steepest descent.
Enough to check when e(x,y) = ax +by +c
The Siddhagad Area
Its Contour Map
Contours and contour-flows
100 95 gentle
plain
ridge
slope
valley narrow
convergence
divergence
90 85
A sample Topo-sheet
Gudwanwadi reservoir.
A close-up
Decomposition
A4 A5
p1
R1 p2 A1 A2
A3
R2
Objective: Divide the domain into
sub-domains, each of reasonable size.
Select suitable points and prepare differential watersheds.
Reservoirs R1 and R2. Special pointsp1 and p2. A1 =WS(p1),A2,A3 =WS(R1)−A1 and so on.
Catchment ofR1 =A1+A2+A3. Catchment R2 =WS(R2)−Catchment(R1).
Attributes of eachAi area, crops, soil, rainfall and so on.
Manar in Hingoli
Watersheds
A Watershed decomposition
The Watershed
a smallvolumetric unit for analysis.
includes static data such as
I geology
I wells and discharges dynamic data such as:
I weather data land and water use.
I farms, factories, wells etc.
Demarcation
Along ridge lines enclosing surface water flow.
Objective
Daregaon
Daregaon
83
90 126
39
58 68
66 53
85 139
74 4
69 26
2
97
59
70 24
1 27
99 146
43
100
60 44
65 49 136
52 111
29
89 87
164
75
46
77 57 157
56 104 131
152
55
96 116
35 174
163
36
47 48 177
81
50
180 17
73 151
173
23 3132 30
67 40 162
179 172 164
119 125
64 72 117
181
129
63 41 142
162
187 185
71 62 127 143 148
54 178
120 124
37 21
76 128
78 19 155
183 20
34
141
106 138
150 173 161
175
84 107 135
42 149
105 160
93
165 156
171
91 167
118 145144
79 88 92 131 132
109 51
170
114 186 153
61 188
98 159
94 137
134
22
166 168
101
16
121 123
103 122
9
112
5 179
18 15
115
158
12 162
38
140 3
130 165
184
75°29'0"E 75°28'0"E
75°27'0"E
20°5'0"N 20°5'0"N
20°4'0"N 20°4'0"N
.
Legend Lineament Drainage Village Gat No.
High Priority Moderate Priority Low Priority
Limited Scope (Good for Soil Conservation)
0 0.250.5 1 1.5 2
Kilometers
Map Showing Prioritization for Artificial Recharge Distict - Aurangabad, Taluka:- Phulambri, Village - Daregaon
Daregaon
.
0 0.225 0.45 0.9
Kilometers 1:20,000 SCALE - ACTIONPLAN MAP (Watershed No:- GP-8/4/14)
PREPARED BY::
Maharashtra Remote Sensing Applications Centre, Dept. of Planning,Nagpur,
Govt. of Maharashtra.
And GSDA,Pune DATA SOURCES::
Village Map:Directorate of Land Records Linaments/Dyke:Derived from SatelliteData MRSAC, Actionplan: MRSAC Contour 5mt:Derived from SRTM data MRSAC, Watershed -AISLUS & GSDA, Drainage:GSDA,Pune
Village-Daregaon ,Taluka -Fulambari, District -Aurangabad
Location Map 710
685
690
695
680
675 715
725720 665
660 655
650
745
715
735
725
735
730 GP-8/ 04/14
GP-8/ 04/12
D a r e g a o n D a r e g a o n
83
90 126
39
58 68
66 53
85 139
74 4
69 26
2
97
59
70 24
1 27
99 146
43
100
60 44
65 136
177
52
81 111
29
50
180 17
89 87
164
73 151
75 77
57 157
56 104 131
40 152
164
119
55 96
116 117
41 35 162
187 143 185
174 37
163
36 19 155
183 20
34
106 175173
105 494847
173
46 23 323133 30
67 162
179 172
125
64 72 181
129
63 142
71 62 127 148
54 178
120 124
21
76 128
78 141 138
150 161
84 107 135
42 149
160
93
165 156
171
91 167
118 145144
79 88
173
92 131 132
109 51
170
114 186 153
61 188
98 159
94 137
134 22 166 168
101
16
121 123
103 182
122 9
112
5
133 179
15 18
113 169
115
158
127 162
38 29
140 3 13
108 130
165 158
184 28
147
75°29'0"E 75°29'0"E
75°28'30"E 75°28'30"E
75°28'0"E 75°28'0"E
75°27'30"E 75°27'30"E
75°27'0"E 75°27'0"E
75°26'30"E 75°26'30"E
75°26'0"E 75°26'0"E
20°5'30"N 20°5'30"N
20°5'0"N 20°5'0"N
20°4'30"N 20°4'30"N
20°4'0"N 20°4'0"N
20°3'30"N 20°3'30"N
PREPARED FOR::
Vasundhara Watershed Development Agency, Maharashtra, Pune-1 AndDirector of Soil and Water Conservation Maharashtra, Pune-1
Sillod Kannad Vaijapur
Paithan GangapurAurangabad
Fulambari Soegaon Khuldabad
Soegaon
Part of Jalna District Part of Vaijapur
PuneBid Nashik
Solapur Satara
Jalgaon
Thane Yavatmal
Gadchiroli Jalna
Latur Amravati
Sangli Nagpur Nanded Dhule
Buldana Chandrapur
Ratnagiri Raigarh
Kolhapur Gondiya
Osmanabad Nandurbar
Sindhudurg Bhandara Legend
Linaments/Dyke Contour 5 Meter Watershed Boundary Survey/Gat No. Boundary Village Boundary Drainage Line Treatment
Gully Plug or LBS Earthen Nalla Bund/ Gabian Bandhara Nala Desilting/C.N.B./K.T.
Area Treatment Dry land Agriculture/Contour Bunding/ Farmpond Afforestation/ Dry Land Horticulture/Plantation CCT/Deep CCT/WAT/Forest Pond Compartment Bunding/Graded Bunding/Fram Pond/Well Recharge River/ Waterbody
Village Area Page Size:A1
JALYUKT SHIVAR ABHIYAN (2017-18)
In Map Show Existing Activities with Red Colour and Proposed Activities
with Green Colour
(For Official Use Only)
The mathematics, data, entities and quantities
0.0 20
0.2
18 16 0.4
14 0.6
12 0.8
X10 Z
1.0
8 6 0
2 1.2
6 4
4 8
10 1.4
2 12
Y 16 14
1.6
0 18 20 1.8
2.0
The DTM or DEM: terrain model/elevation model is a representation of the terrain in a particular area.
The Digital Terrain/Elevation model
XY−Domain (xi,yi)
zi
Basic grid in the 2D-plane as an index set,with adjacency association ofz-values for each point, to define 3D points, edges, triangles and adjacency.
The Attributes and Computation
The DTM or DEM: terrain model/elevation model is a representation of the terrain in a particular area.
Attributes of the DTM-soil, geology, land-use, land-cover.
Regions-subsets of the DTM, to represent watersheds, flows, etc.
Functions and Computations: to simulate various physical quantities and their dynamics.
I Infiltration: the process of rainwater moving down to groundwater.
I Drainage lines: The development of streams due to rainfall.
I Surface flow: a composite model of surface flow of water and infiltration which may include time to flow, movement of solids
Lets Compute Drainage
If a drop falls at point (i,j) then how does it move?
We consider the 8-neighbours of the point.
8−way adjacency
The flow gets distributed relative to the height
Here is an example:
1.1 1.5 1.6 1.3 1.4 1.7 1.3 1.3 1.5 Hypothesis: Only lower, and in proportion to the height differences.
3/6 0 0
1/6 0 0
1/6 1/6 0
And this continues recursively downwards.
and Infiltration
The slope values (×10−3).
2.1 2.5 2.6 7.3 9.1 8.0 1.3 1.3 1.5 Hypothesis: Infiltration depends on slope.
0.1 0.09 0.09
0 0 0
0.2 0.2 0.15 More complicated models:
Ikharicha pada
Ikharicha pada
A watershed*
*Thanks to FES.org
Coming back-mywatershed
V−weirs Rain−gauges
Suppose that we have installed appropriate rain-gauges and V-notch weirs.
Suppose that we have good geological and GW data.
Can we achieve stating a
water-budget for mywatershed?
Likely not. Most natural phenomena too complicated to model.
A good model will always have predictive value.
