diff --git a/description.lua b/description.lua
index 0553e83..782b90e 100644
--- a/description.lua
+++ b/description.lua
@@ -1,4 +1,4 @@
-version = "0.8.3"
+version = "0.8.5"
 license = "GPL"
 package = "sysdyn"
 depends = "terrame (>= 2.0), sci (>= 0.3)"
diff --git a/log/Dam-chart-1.bmp b/log/Dam-chart-1.bmp
new file mode 100644
index 0000000..f4f18e8
Binary files /dev/null and b/log/Dam-chart-1.bmp differ
diff --git a/log/Dam-chart-2.bmp b/log/Dam-chart-2.bmp
new file mode 100644
index 0000000..dc60147
Binary files /dev/null and b/log/Dam-chart-2.bmp differ
diff --git a/log/random-walk.png b/log/random-walk.png
index 00e4f99..fbaf73b 100644
Binary files a/log/random-walk.png and b/log/random-walk.png differ
diff --git a/lua/Dam.lua b/lua/Dam.lua
new file mode 100644
index 0000000..8cdcdac
--- /dev/null
+++ b/lua/Dam.lua
@@ -0,0 +1,68 @@
+--- A water in the dam model.
+-- @arg data.water The initial stock of water measured in m³. The initial value is 5,000,000,000.
+-- @arg data.inFlow1 The flow of water into the dam each first season. The default is 2e9.
+-- @arg data.inFlow2 The flow of water into the dam each second season. The default value is 1.5e9.
+-- @arg data.currentYear The starting year. The default value is 1950.
+-- @arg data.population The total amount of inhabitants. The default value is 1e5.
+-- @arg data.consumePerPerson The total amount of water per inhabitant. The default value is 10.
+-- @arg data.kWh2cubicMeters The total amount of kWh produced by cubic meters. The default value is 100.
+-- @arg data.growth The comsumption amount of kWh produced by cubic meters. The default value is 100.
+-- @arg data.countYear The flag in which defines whether count or not the years . The default value is false.
+-- @arg data.changedYear The year in which water values change. The default value is 1970.
+-- @arg data.finalTime The final time of the simulation in months. The default value is 1000.
+Dam = Model{
+	water = 5e9,
+	inFlow1 = 2e9,
+	inFlow2 = 1.5e9,
+	population = 1e5,
+	consumePerPerson = 10,
+	kWh2cubicMeters = 100,
+	growth = 0.05,
+	countYear = false,
+	changedYear= 1970,
+	currentYear = 1950,
+	finalTime = 1000,
+	execute = function(self) -- each time step
+		local outFlow = self.population * self.consumePerPerson * self.kWh2cubicMeters -- update outflow
+		self.water = self.water - outFlow -- update water
+
+		if self.water <= 0 then -- water amount less than zero
+			self.water = 0
+		elseif self.water > 5e9 then -- water amount more than dam capacity
+			self.water = 5e9
+		end
+
+		if (self.countYear == true) then
+			if (self.timer:getTime()%12 == 0) then -- every each year increments current year
+				self.currentYear = self.currentYear + 1
+				if (self.currentYear == self.changedYear) then -- when changedYear equal to currentYear
+					self.inFlow1 = self.inFlow1/2
+					self.inFlow2 = self.inFlow2/2
+				end
+			end
+		end
+	end,
+
+	init = function (self)
+		self.chart = Chart{
+			target = self,
+			select = "water"
+		}
+
+		self.timer = Timer{
+			Event{action = self, priority = 'high'},
+			Event{start = 1, period = 12, action = function()
+				self.water = self.water + self.inFlow1 -- first season in first semester
+			end},
+			Event{start = 7, period = 12, action = function()
+				self.water = self.water + self.inFlow2 -- second season in second semester
+			end},
+			Event{period = 12, action = function()
+				self.consumePerPerson = self.consumePerPerson*(1 + self.growth) -- every year add 5%
+			end},
+			Event{action = self.chart}
+		}
+
+	end
+}
+
diff --git a/lua/Tub.lua b/lua/Tub.lua
index 3b395d6..ce54608 100644
--- a/lua/Tub.lua
+++ b/lua/Tub.lua
@@ -24,7 +24,7 @@ Tub = Model{
 
 		model.timer = Timer{
 			Event{action = model},
-			Event{start = 10, period = 10, action = function()
+			Event{period = 10, action = function()
 				model.water = model.water + model.inFlow
 			end},
 			Event{action = model.chart}
diff --git a/tests/Dam.lua b/tests/Dam.lua
new file mode 100644
index 0000000..8bd75e9
--- /dev/null
+++ b/tests/Dam.lua
@@ -0,0 +1,19 @@
+-- Test file for Dam.lua
+-- Author: Gilberto Camara and Pedro R. Andrade
+
+return{
+	Dam = function(unitTest)
+		local model = Dam{}
+
+		model:run()
+
+		unitTest:assertSnapshot(model.chart, "Dam-chart-1.bmp", 0.20)
+
+		model = Dam{countYear = true}
+
+		model:run()
+
+		unitTest:assertSnapshot(model.chart, "Dam-chart-2.bmp", 0.12)
+	end,
+}
+
diff --git a/tests/RandomWalk.lua b/tests/RandomWalk.lua
index 5b68447..926cb7b 100644
--- a/tests/RandomWalk.lua
+++ b/tests/RandomWalk.lua
@@ -6,7 +6,7 @@ return{
 		local r = RandomWalk{}
 		r:run()
 
-		unitTest:assertEquals(r.value, 2)
+		unitTest:assertEquals(r.value, -4)
 		unitTest:assertSnapshot(r.chart, "random-walk.png", 0.1)
 	end,
 }